Showing papers by "Baylor College of Medicine published in 1991"
TL;DR: A fragile X site-induced breakpoint cluster region that exhibits length variation in fragile X chromosomes is identified and localization of the brain-expressed FMR-1 gene to this EcoRI fragment suggests the involvement of this gene in the phenotypic expression of the fragile X syndrome.
3,290 citations
TL;DR: It is demonstrated that src is not required for general cell viability (possibly because of functional overlap with other tyrosine kinases related to src) and an essential role for src in bone formation is uncovered.
2,086 citations
TL;DR: The risk of expansion during oogenesis to the full mutation associated with mental retardation increases with the number of repeats, and this variation in risk accounts for the Sherman paradox.
2,040 citations
TL;DR: A randomized, double-blind trial in patients with sepsis and a presumed diagnosis of gram-negative infection was conducted in this article, where the patients received either a single 100mg intravenous dose of HA-1A or placebo.
Abstract: Background HA-1A is a human monoclonal IgM antibody that binds specifically to the lipid A domain of endotoxin and prevents death in laboratory animals with gram-negative bacteremia and endotoxemia Methods To evaluate the efficacy and safety of HA-1A, we conducted a randomized, double-blind trial in patients with sepsis and a presumed diagnosis of gram-negative infection The patients received either a single 100-mg intravenous dose of HA-1A(in 35 g of albumin) or placebo (35 g of albumin) Other interventions, including the administration of antibiotics and fluids, were not affected by the study protocol Results Of 543 patients with sepsis who were treated, 200 (37 percent) had gram-negative bacteremia as proved by blood culture For the patients with gram-negative bacteremia followed to death or day 28, there were 45 deaths among the 92 recipients of placebo (49 percent) and 32 deaths among the 105 recipients of HA-1A (30 percent; P = 0014) For the patients with gram-negative bacteremia and sho
1,512 citations
TL;DR: Intercrossing of heterozygotes from 24 strains that express beta-galactosidase identified 9 strains in which homozygosity leads to an embryonic lethality, suggesting that a substantial proportion of mammalian genes identified by this approach are not essential for development.
Abstract: A general strategy for selecting insertion mutations in mice has been devised. Constructs lacking a promoter and including a beta-galactosidase gene, or a reporter gene encoding a protein with both beta-galactosidase and neomycin phosphotransferase activity, were designed so that activation of the reporter gene depends on its insertion within an active transcription unit. Such insertion events create a mutation in the tagged gene and allow its expression to be followed by beta-galactosidase activity. Introduction of promoter trap constructs into embryonic stem (ES) cells by electroporation or retroviral infection has led to the derivation of transgenic lines that show a variety of beta-galactosidase expression patterns. Intercrossing of heterozygotes from 24 strains that express beta-galactosidase identified 9 strains in which homozygosity leads to an embryonic lethality. Because no overt phenotype was detected in the remaining strains, these results suggest that a substantial proportion of mammalian genes identified by this approach are not essential for development.
1,424 citations
TL;DR: FMR-1 mRNA was absent in the majority of male fragile X patients, suggesting a close involvement of this gene in development of the syndrome, and the methylation status of the BssHII site at the CpG island was studied.
1,397 citations
TL;DR: It is demonstrated that failure to recognize the molecular duplication can lead to misinterpretation of marker genotypes for affected individuals, identification of false recombinants, and incorrect localization of the disease locus.
1,293 citations
Journal Article•
TL;DR: A method enabling rapid localization of STRs and determination of their flanking DNA sequences was developed, thus simplifying the identification of polymorphic STR loci.
Abstract: Tandemly reiterated sequences represent a rich source of highly polymorphic markers for genetic linkage, mapping, and personal identification. Human trimeric and tetrameric short tandem repeats (STRs) were studied for informativeness, frequency, distribution, and suitability for DNA typing and genetic mapping. The STRs were highly polymorphic and inherited stably. A STR-based multiplex PCR for personal identification is described. It features fluorescent detection of amplified products on sequencing gels, specific allele identification, simultaneous detection of independent loci, and internal size standards. Variation in allele frequencies were explored for four U.S. populations. The three STR loci (chromosomes 4, 11, and X) used in the fluorescent multiplex PCR have a combined average individualization potential of 1/500 individuals. STR loci appear common, being found every 300-500 kb on the X chromosome. The combined frequency of polymorphic trimeric and tetrameric STRs could be as high as 1 locus/20 kb. The markers should be useful for genetic mapping, as they are sequence based, and can be multiplexed with the PCR. A method enabling rapid localization of STRs and determination of their flanking DNA sequences was developed, thus simplifying the identification of polymorphic STR loci. The ease by which STRs may be identified, as well as their genetic and physical mapping utility, give them the properties of useful sequence tagged sites (STSs) for the human genome initiative.
1,196 citations
Journal Article•
TL;DR: Endothelium‐dependent relaxation of blood vessels is produced by a large number of agents (e.g., acetylcholine, ATP and ADP, substance P, bradykinin, histamine, thrombin, serotonin).
Abstract: Since the description of the essential role of the endothelium in mediating relaxations due to acetylcholine in mammalian arteries, it has become obvious that endothelial cells release several relaxing and contracting substances. The release is activated by a variety of agents including circulating hormones, autacoids, and products liberated by aggregating platelets, but also by changes in shear stress exerted by the blood. There is strong evidence that the major endothelium-derived relaxing factor (EDRF) is the free radical nitric oxide (NO) formed enzymatically from L-arginine. Endothelium-dependent relaxations caused by EDRF are induced through increases in the activity of soluble guanylate cyclase in the smooth muscle. Other relaxing factors, such as prostacyclin and endothelium-derived hyperpolarizing factor (EDHF) contribute to endothelium-dependent relaxations. Beside the recently described and chemically identified peptide endothelin, at least two other endothelium-derived contracting factors appear to exist. The mechanisms by which endothelium-derived contracting factors activate vascular smooth muscle are not yet clear. In certain clinical situations an impairment of the production of EDRF in face of a maintained or augmented release of contracting factors may contribute to the occurrence of localized vasospasm or generalized increases in peripheral resistance.
1,193 citations
TL;DR: An in utero fetal weight model from a population of 392 predominantly middle-class white patients with certain menstrual histories is developed, with a gradual increase in fetal weight from 35 g at 10 weeks to 3,619 g at 40 weeks, with uniform variance throughout gestation.
Abstract: Regression analysis was used to develop an in utero fetal weight model from a population of 392 predominantly middle-class white patients with certain menstrual histories. There was a gradual increase in fetal weight from 35 g at 10 weeks to 3,619 g at 40 weeks, with uniform variance of +/- 12.7% (1 standard deviation) throughout gestation. When tested against the estimated weights of 1,771 chromosomally normal fetuses between 14 and 21 weeks, the mean percent difference was 0.8% and the average absolute percent error was 3.3%. When compared with actual delivery data for 163 fetuses in the group, the mean percent difference was 0.8% and the average absolute percent error was 1.1%. These data are compared with other prenatal weight curves obtained at ultrasound and with data from several large postnatal weight studies.
1,034 citations
TL;DR: The prevalence of H. pylori infection among 485 healthy asymptomatic volunteers between the ages of 15 and 80 residing in the Houston metropolitan area was investigated and it was found that having pets was associated with a lower frequency, but this was highly associated with higher socioeconomic status.
TL;DR: Botulinum toxin type A, one of the most lethal biologic toxins, has been found to be of therapeutic value in the treatment of a variety of neurologic and ophthalmologic disorders.
Abstract: BOTULISM had been recognized by the 18th century, but the observation that a toxin produced by an anaerobic organism might be responsible for food poisoning was not made until 1897.1 Although seven immunologically distinct toxins have since been identified, only types A, B, and E have been linked to cases of botulism in humans.2 , 3 Botulinum toxin type A (hereafter referred to as botulinum toxin), one of the most lethal biologic toxins, has been found to be of therapeutic value in the treatment of a variety of neurologic and ophthalmologic disorders.4 The Food and Drug Administration recently approved botulinum toxin (Oculinum) . . .
TL;DR: It is concluded that at sites of chronic inflammation, ELAM-1 may function as a skin vascular addressin, a tissue-selective endothelial cell-adhesion molecule for skin-homing memory T lymphocytes.
Abstract: Endothelial cell leukocyte adhesion molecule-1 (ELAM-1) has been described as an inducible endothelial cell-adhesion molecule for neutrophils, and is believed to have a key role in the extravasation of these cells at sites of acute inflammation. Here we report that ELAM-1-transfected COS cells also bind a unique skin-associated subset of circulating memory T cells defined by the expression of the cutaneous lymphocyte-associated antigen. T cells expressing this antigen bind at least as well as neutrophils to expressed ELAM-1, whereas other lymphocytes in the peripheral blood bind poorly, or not at all. Immunohistological survey of chronically inflamed tissue specimens revealed that vascular expression of ELAM-1 occurs at cutaneous sites in preference to noncutaneous sites. We conclude that at sites of chronic inflammation, ELAM-1 may function as a skin vascular addressin, a tissue-selective endothelial cell-adhesion molecule for skin-homing memory T lymphocytes.
TL;DR: A gene has now been isolated from the critical region on Xp22.3 to which Kallmann's syndrome locus has been assigned: this gene escapes X inactivation, has a homologue on the Y chromosome, and shows an unusual pattern of conservation across species.
Abstract: Kallmann's syndrome (clinically characterized by hypogonadotropic hypogonadism and inability to smell) is caused by a defect in the migration of olfactory neurons, and neurons producing hypothalamic gonadotropin-releasing hormone. A gene has now been isolated from the critical region on Xp22.3 to which the syndrome locus has been assigned: this gene escapes X inactivation, has a homologue on the Y chromosome, and shows an unusual pattern of conservation across species. The predicted protein has significant similarities with proteins involved in neural cell adhesion and axonal pathfinding, as well as with protein kinases and phosphatases, which suggests that this gene could have a specific role in neuronal migration.
TL;DR: Kupffer cells are the predominant source of reactive oxygen formed during the initial reperfusion period and that Kupffer cell activity (including reactive oxygen formation) contributes to reperfusions injury in the liver in vivo.
Abstract: The hypothesis that Kupffer cells and infiltrating neutrophils generate reactive oxygen in the hepatic sinusoids and may contribute to ischemia-reperfusion injury in the liver was investigated in a model of partial no-flow ischemia and reperfusion in male Fischer rats in vivo. During the reperfusion period of 60 min, plasma concentrations of glutathione disulfide (GSSG; index of oxidant stress) increased from 1.62 +/- 0.20 microM glutathione (GSH) equivalents to maximal values of 11.82 +/- 1.45 (45 min ischemia), 24.19 +/- 2.35 (60 min ischemia), and 70.20 +/- 7.8 (120 min ischemia). The basal tissue GSSG content in the postischemic lobes (0.19 +/- 0.02 nmol GSH eq/mg protein) increased by 50-100%. Although the number of neutrophils in liver and lung increased by 3- to 10-fold during reperfusion, there was no positive correlation between the number of neutrophils and the GSSG concentrations measured in plasma or tissue. However, activation of Kupffer cells with high doses of retinol or with Propionibacterium acnes significantly enhanced plasma GSSG levels, while inactivation of Kupffer cells with methyl palmitate or gadolinium chloride significantly attenuated the increase of plasma GSSG. Inactivation of Kupffer cells protected the liver significantly against ischemia-reperfusion injury. It is concluded that Kupffer cells are the predominant source of reactive oxygen formed during the initial reperfusion period and that Kupffer cell activity (including reactive oxygen formation) contributes to reperfusion injury in the liver in vivo.
TL;DR: It is demonstrated that two patients with spontaneous cases of Dowling-Meara EBS have point mutations in a critical region in one (K14) of two basal keratin genes, suggesting that the basis for the phenotype in this patient resides in this point mutation.
TL;DR: The findings show that the prevalence of H pylori infection is high among young Peruvian children and that the municipal water supply seems to be an important source of infection among Lima children from families of both low and high socioeconomic status.
TL;DR: A nonsense ochre mutation is identified within a 67-base-pair exon of the rd PDE beta-subunit gene that truncates the normal gene product, eliminating more than one-half of the peptide chain, including the putative catalytic domain.
Abstract: Retinal degeneration in the mouse mutant, rd, was previously shown to be a disorder of cyclic nucleotide metabolism involving a deficiency in the activity of the rod photoreceptor cGMP phosphodiesterase (PDE). We have characterized the normal and rd PDE beta-subunit gene, and their respective transcripts, by PCR and direct sequence analysis. We show that the gene consists of at least 22 exons ranging in size from 48 base pairs to several hundred base pairs, covering greater than 25 kilobases. Within a 67-base-pair exon of the rd PDE beta-subunit gene, we identified a nonsense ochre mutation (a C----A transversion in codon 347) that truncates the normal gene product, eliminating more than one-half of the peptide chain, including the putative catalytic domain. The consequences of the truncation are consistent with the observed phenotypes in rd mice heterozygous and homozygous for the disorder. The nonsense mutation was also found in another related and in six unrelated strains displaying the rd phenotype, indicating that the rd allele arose from a single genetic event. The results strongly argue for the nonsense mutation being responsible for retinal degeneration in the rd mouse.
TL;DR: The oocyte system can accurately express ligand-gated ion channels because mouse muscle nAChRs expressed in oocytes display pharmacological properties similar to those reported for these receptors expressed on BC3H-1 cells.
Abstract: A family of genes has been identified that encodes subunits of nicotinic acetylcholine receptors (nAChRs) and is expressed in the nervous system. Functional neuronal nAChRs can be expressed in Xenopus oocytes by injection of RNA encoding 1 of 2 different beta-subunits (beta 2, beta 4) in pairwise combination with RNA encoding 1 of 3 different alpha-subunits (alpha 2, alpha 3, alpha 4). We examined the sensitivity of these 6 different alpha- beta-subunit combinations to the nicotinic agonists ACh, nicotine, cytisine, and 1,1-dimethyl-4-phenylpiperazinium (DMPP). Each subunit combination displayed a distinct pattern of sensitivity to these 4 agonists. The alpha 2 beta 2 combination was 5-fold more sensitive to nicotine than to acetylcholine, while the alpha 3 beta 2 combination was 17-fold less sensitive to nicotine than to ACh, and the alpha 3 beta 4 combination was equally sensitive to both nicotine and ACh. nAChRs composed of alpha 2, alpha 3, or alpha 4 in combination with beta 2 were 14-100-fold less sensitive to cytisine than to ACh. In contrast, nAChRs composed of alpha 2, alpha 3, or alpha 4 in combination with beta 4 were 3-17-fold more sensitive to cytisine than to ACh. The alpha 2 beta 2, alpha 3 beta 2, and alpha 3 beta 4 combinations were each equally sensitive to DMPP and ACh, while the alpha 2 beta 4, alpha 4 beta 2, and alpha 4 beta 4 combinations were 4-24-fold less sensitive to DMPP than to ACh. We also demonstrated that these differences are neither a consequence of variation in the relative amounts of RNA injected nor an artifact of oocyte expression. The oocyte system can accurately express ligand-gated ion channels because mouse muscle nAChRs expressed in oocytes display pharmacological properties similar to those reported for these receptors expressed on BC3H-1 cells. We conclude that both the alpha- and the beta-subunits contribute to the pharmacological characteristics of neuronal nAChRs.
TL;DR: In vitro, dopamine faithfully mimicked the effect of progesterone by causing a translocation of chicken progestersone receptor (cPR) from cytoplasm to nucleus, and a serine residue in the cPR was identified that is not necessary for progester one-dependent activation of cPR, but is essential for dopamine activation of this receptor.
Abstract: The current view of how steroid hormone receptors affect gene transcription is that these receptors, on binding ligand, change to a state in which they can interact with chromatin and regulate transcription of target genes. Receptor activation is believed to be dependent only on this ligand-binding event. Selected steroid hormone receptors can be activated in a ligand-independent manner by a membrane receptor agonist, the neurotransmitter dopamine. In vitro, dopamine faithfully mimicked the effect of progesterone by causing a translocation of chicken progesterone receptor (cPR) from cytoplasm to nucleus. Dual activation by progesterone and dopamine was dissociable, and a serine residue in the cPR was identified that is not necessary for progesterone-dependent activation of cPR, but is essential for dopamine activation of this receptor.
TL;DR: As compared with intravesical doxorubicin, immunotherapy with BCG provides improved protection against the recurrence of superficial bladder cancer.
Abstract: Background. In carcinoma of the bladder, both intravesical chemotherapy and immunotherapy can induce tumor regression and reduce the rate of recurrence, but the relative merits of these two therapies are unclear. We conducted a multi-institutional study to address this question. Methods. Patients with rapidly recurrent (stage Ta or T1) or in situ transitional-cell carcinoma of the bladder were randomly assigned to receive either doxorubicin administered intravesically or bacille Calmette–Guerin (BCG) administered both intravesically and percutaneously. The 262 eligible patients were followed for a median of 65 months. Complete responses to treatment of carcinoma in situ were confirmed by biopsy and cytologic analysis of the urine. Results. For patients with Ta and T1 tumors without carcinoma in situ, the estimated probability of being disease free at five years was 17 percent after doxorubicin, as compared with 37 percent after immunotherapy with BCG (P = 0.015). The median times to treatment fai...
TL;DR: The isolation and characterization of its murine homologue (Xist) is reported which localizes to the mouse X inactivation centre region and is the first murine gene found to be expressed from the inactive X chromosome and may be associated with a protein product.
Abstract: IN mammals, equal dosage of gene products encoded by the X chromosome in male and female cells is achieved by X inactivation. Although X-chromosome inactivation represents the most extensive example known of long range cis gene regulation, the mechanism by which thousands of genes on only one of a pair of identical chromosomes are turned off is poorly understood. We have recently identified a human gene (XIST) exclusively expressed from the inactive X chromosome1. Here we report the isolation and characterization of its murine homologue (Xist) which localizes to the mouse X inactivation centre region and is the first murine gene found to be expressed from the inactive X chromosome. Nucleotide sequence analysis indicates that Xist may be associated with a protein product. The similar map positions and expression patterns for Xist in mouse and man suggest that this gene may have a role in X inactivation.
TL;DR: The 3D structure of the Maltodextrin-binding protein (Mr = 40,622) with bound maltose has been obtained by crystallographic analysis at 2.8-A resolution as discussed by the authors.
TL;DR: It is concluded that balloon expandable stents are useful in selected postoperative stenoses in congenital heart disease.
Abstract: BACKGROUNDBalloon expandable intravascular stents have been used to support vessel walls in coronary and peripheral arteries in adults. The purpose of this study was to examine the efficacy and safety of these stents in the treatment of congenital heart disease.METHODS AND RESULTSForty-five stents were placed in 30 patients, who were 0.2-30.2 years old (weight, 3.5-76 kg). Patients with areas of stenosis that were difficult to approach surgically were chosen. Stents were mounted over balloons and placed by standard catheterization techniques. Twenty-three patients had branch pulmonary artery stenosis. Thirty-six stents were placed successfully and had reduced pressure gradients from 50.6 +/- 24 to 15.9 +/- 13.4 mm Hg. Five patients had stents placed after atrial surgery: three in obstructed Fontan repairs, one at the superior vena cava-right atrial junction after sinus venous defect repair, and one at the site of a Glenn shunt. Atrial stents reduced pressure gradients from 9.8 +/- 8.2 to 2.0 +/- 2.6 mm Hg...
TL;DR: A national system for surveillance of congenital CMV disease was established; its goals are to characterize trends over time, to identify risk groups, and to lay the groundwork for evaluation of future intervention programs.
Abstract: Each year in the United States, 30,000 to 40,000 infants are born congenitally infected with cytomegalovirus (CMV), and more than 9,000 of these children suffer permanent sequelae. The purpose of this workshop was to present and discuss current information on the epidemiology, diagnosis, treatment, and prevention of CMV disease in mothers and their infants. The participants concluded that congenital CMV disease is a significant public health problem that, to date, has been largely ignored. They also agreed that certain child-rearing practices, such as the common use of day-care centers and breast-feeding, have changed the epidemiology of CMV in the United States and that the next decade may bring an increase in congenital CMV disease in certain groups. Therefore, a national system for surveillance of congenital CMV disease was established; its goals are to characterize trends over time, to identify risk groups, and to lay the groundwork for evaluation of future intervention programs. In addition, the surveillance system will be used to educate the medical and lay communities about congenital CMV disease and to facilitate collaborative efforts in research.
TL;DR: The concept that LECAM-1 is a neutrophil adhesion molecule that participates in the adherence of unstimulated neutrophils to cytokine-stimulated endothelial cells under conditions of flow, and is then lost from the neutrophIL surface coincident with the engagement of CD18-dependent mechanisms leading to transendothelial migration is supported.
Abstract: Monoclonal antibodies recognizing CD18, CD11a, CD11b, and neutrophil lectin adhesion molecule 1 (LECAM-1), i.e., the human homologue of the murine MEL-14 antigen, were used to assess the relative contribution of these glycoproteins to neutrophil-endothelial adhesion. Under static conditions, the adhesion of neutrophils to IL-1-stimulated human umbilical vein endothelial cell (HUVEC) monolayers was inhibited by antibodies to CD18, CD11a, and the neutrophil LECAM-1, and the effect of combining anti-LECAM-1 and anti-CD11a was almost additive. Under flow at a wall shear stress 1.85 dyn/cm2, a condition where CD18-dependent adhesion is minimal, anti-LECAM-1 inhibited adhesion by greater than 50%. Chemotactic stimulation of neutrophils induced a rapid loss of LECAM-1 from the neutrophil surface, and the level of neutrophil surface LECAM-1 was closely correlated with adhesion under flow. Neutrophils contacting the activated endothelial cells for 30 min lost much of their surface LECAM-1, a phenomenon induced by a soluble factor or factors released into the medium by the stimulated monolayers, and a high percentage migrated through the HUVEC monolayer. This migration was almost completely inhibited by anti-CD18, but was unaffected by antibodies to neutrophil LECAM-1. These results support the concept that LECAM-1 is a neutrophil adhesion molecule that participates in the adherence of unstimulated neutrophils to cytokine-stimulated endothelial cells under conditions of flow, and is then lost from the neutrophil surface coincident with the engagement of CD18-dependent mechanisms leading to transendothelial migration.
TL;DR: The results demonstrate that, in patients in whom thrombolytic therapy fails to induce reperfusion, the presence of coronary collateral vessels at the onset of myocardial infarction is associated with limitation of infarct size as assessed enzymatically and with improved ventricular function on discharge as assessed by LVEF.
Abstract: BACKGROUNDThe influence of coronary collateral vessels on infarct size in humans remains controversial, partly because no previous study has examined the impact of collaterals present at the onset of acute myocardial infarction on infarct sizeMETHODS AND RESULTSThe present study used the data base of the Thrombolysis in Myocardial Infarction (TIMI) Phase I trial to correlate the presence or absence of angiographically documented collaterals in the initial hours of myocardial infarct evolution with the size of the infarct as assessed by serial measurements of serum creatine kinase (CK) To avoid the confounding effects of reperfusion on enzymatic estimates of infarct size, this report is limited to those 125 patients who failed to recanalize at 90 minutes after administration of tissue plasminogen activator or streptokinase Patients with angiographically documented collaterals (group A, n = 51) had significantly lower values of peak serum CK than patients without collaterals (group B, n = 74) (1,877 +/-
TL;DR: Although this trial demonstrated trends supportive of HSD in hypotensive hemorrhagic shock patients requiring surgery, a larger sample size will be required to establish which subgroups of trauma patients might maximally benefit from the prehospital use of a small volume of hyperosmolar solution.
Abstract: The safety and efficacy of 7.5% sodium chloride in 6% dextran 70 (HSD) in posttraumatic hypotension was evaluated in Houston, Denver, and Milwaukee. Multicentered, blinded, prospective randomized studies were developed comparing 250 mL of HSD versus 250 mL of normal crystalloid solution administered before routine prehospital and emergency center resuscitation. During a 13-month period, 422 patients were enrolled, 211 of whom subsequently underwent operative procedures. Three hundred fifty-nine patients met criteria for efficacy analysis, 51% of whom were in the HSD group. Seventy-two per cent of all patients were victims of penetrating trauma. The mean injury severity score (19), Trauma Score plus Injury Severity Score (TRISS) probability of survival, revised trauma scores (5.9), age, ambulance times, preinfusion blood pressure, and etiology distribution were identical between groups. The total amount of fluid administered, white blood cell count, arterial blood gases, potassium, or bicarbonate also were identical between groups. The HSD group had an improved blood pressure (p = 0.024). Hematocrit, sodium chloride, and osmolality levels were significantly elevated in the Emergency Center. Although no difference in overall survival was demonstrated, the HSD group requiring surgery did have a better survival (p = 0.02), with some variance among centers. The HSD group had fewer complications that the standard treatment group (7 versus 24). A greater incidence of adult respiratory distress syndrome, renal failure, and coagulopathy occurred in the standard treatment group. No anaphylactoid nor Dextran-related coagulopathies occurred in the HSD group. Although this trial demonstrated trends supportive of HSD in hypotensive hemorrhagic shock patients requiring surgery, a larger sample size will be required to establish which subgroups of trauma patients might maximally benefit from the prehospital use of a small volume of hyperosmolar solution. This study demonstrates the safety of administering 250 mL 7.5% HDS to this group of patients.
TL;DR: A stereoselective addition-elimination or SN2 mechanism of the enzyme is proposed with the zinc atom and the Glu and Asp residues playing key roles and a molecular explanation of a hereditary disease caused by several point mutations of an enzyme is presented.
Abstract: The crystal structure of a murine adenosine deaminase complexed with 6-hydroxyl-1,6-dihydropurine ribonucleoside, a nearly ideal transition-state analog, has been determined and refined at 2.4 angstrom resolution. The structure is folded as an eight-stranded parallel alpha/beta barrel with a deep pocket at the beta-barrel COOH-terminal end wherein the inhibitor and a zinc are bound and completely sequestered. The presence of the zinc cofactor and the precise structure of the bound analog were not previously known. The 6R isomer of the analog is very tightly held in place by the coordination of the 6-hydroxyl to the zinc and the formation of nine hydrogen bonds. On the basis of the structure of the complex a stereoselective addition-elimination or SN2 mechanism of the enzyme is proposed with the zinc atom and the Glu and Asp residues playing key roles. A molecular explanation of a hereditary disease caused by several point mutations of an enzyme is also presented.
TL;DR: The ratio of the velocity of the catalyzed reaction to that of the uncatalyzed reaction increases as the quantity of GSH2/GSSG increases and approaches a constant, limiting value at [GSH]2/[G SSG] greater than 1 mM, suggesting that a reduced, dithiol form of PDI is required for optimum activity.
Abstract: The velocity of the oxidative renaturation of reduced ribonuclease A catalyzed by protein disulfide isomerase (PDI) is strongly dependent on the composition of a glutathione/glutathione disulfide redox buffer. As with the uncatalyzed, glutathione-mediated oxidative folding of ribonuclease, the steady-state velocity of the PDI-catalyzed reaction displays a distinct optimum with respect to both the glutathione (GSH) and glutathione disulfide (GSSG) concentrations. Optimum activity is observed at [GSH] = 1.0 mM and [GSSG] = 0.2 mM. The apparent kcat at saturating RNase concentration is 0.46 +/- 0.05 mumol of RNase renatured min-1 (mumol of PDI)-1 compared to the apparent first-order rate constant for the uncatalyzed reaction of 0.02 +/- 0.01 min-1. Changes in GSH and GSSG concentration have a similar effect on the rate of both the PDI-catalyzed and uncatalyzed reactions except under the more oxidizing conditions employed, where the catalytic effectiveness of PDI is diminished. The ratio of the velocity of the catalyzed reaction to that of the uncatalyzed reaction increases as the quantity [GSH]2/[GSSG] increases and approaches a constant, limiting value at [GSH]2/[GSSG] greater than 1 mM, suggesting that a reduced, dithiol form of PDI is required for optimum activity. As long as the glutathione redox buffer is sufficiently reducing to maintain PDI in an active form [( GSH]2/[GSSG] greater than 1 mM), the rate acceleration provided by PDI is reasonably constant, although the actual rate may vary by more than an order of magnitude. PDI exhibits half of the maximum rate acceleration at a [GSH]2/[GSSG] of 0.06 +/- 0.01 mM.