Biomedical subjects
Publications and source records attributed to J R Roberts.
Therapy for malignant pleural mesothelioma is in a transitional stage. Recent trials of multimodality therapy for this disease suggest that selected patient subgroups may benefit from extensive treatment. This report discusses new approaches to the treatment of malignant pleural mesothelioma. Two case reports are presented.
3-Hydroxy-3-methylglutaryl-CoA (HMG-CoA) lyase is inactivated by diethyl pyrocarbonate (DEPC); activity can be fully restored by incubation with hydroxylamine. Protection against DEPC inactivation is afforded by a substrate analogue, suggesting an active site location for a DEPC target. Included in the inherited defects that map within the HMG-CoA lyase gene is a point mutation that results in an arginine substitution for histidine 233, one of only two invariant histidines. These observations prompted a functional test of the importance of His-233. The mutant lyases H233R, H233A, and H233D were overexpressed in Escherichia coli, isolated, and kinetically characterized. In H233D, DEPC targets one less histidine than was measured using wild-type lyase, supporting the assignment of wild-type lyase His-233 as one of the DEPC targets. Substitution of His-233 results in diminution of activity by approximately 4 orders of magnitude. Km values of the mutant lyases for both substrate HMG-CoA and activator divalent cation (Mg2+ or Mn2+) are comparable to the values measured for wild-type enzyme, indicating that these enzymes retain substantial structural integrity. This conclusion is reinforced by the observation that the affinity label, 2-butynoyl-CoA, stoichiometrically modifies the mutant lyases, indicating that they contain a full complement of active sites. In view of these data suggesting that the structures of these mutant lyases closely approximate that of the wild-type enzyme, their observed 10(4)-fold diminution in catalytic efficiency supports assignment to His-233 of a role in the chemistry of HMG-CoA cleavage.
BACKGROUND: Surgical management of distal duodenal pathology is challenging because of the duodenum's retroperitoneal location and its shared blood supply with the pancreas. For infra-ampullary pathology, surgical treatment may include local excision, pancreaticoduodenectomy, or pancreas-sparing duodenectomy (PSD). PATIENTS AND METHODS: We retrospectively reviewed the management of 24 patients with infra-ampullary duodenal pathology treated by PSD between 1985 and 1994 at The Johns Hopkins Hospital. RESULTS: There were 16 men and 8 women with a mean age of 51.2 +/- 4.4 years. The indications for elective PSD in 19 patients were neoplasms (n = 15), Crohn's disease (n = 2), and other (n = 2). Of the neoplasms, 13 were malignant (11 adenocarcinoma, 1 lymphoma, 1 liposarcoma) and 2 were being (1 villous adenoma, 1 benign stromal tumor). Five patients had PSD as an emergency procedure for penetrating trauma. The mean follow-up is 24.2 +/- 5.8 months (range 1 to 122). In the group undergoing elective PSD, the mean length of operation was 5.3 +/- 0.4 hours, and the estimated blood loss was 569 +/- 121 mL. In the entire series, there was 1 postoperative death from an anastomotic leak and 1 reexploration for anastomotic bleeding. Pancreas-sparing duodenectomy in patients with trauma or benign duodenal pathology resulted in a good outcome in all. In those 11 patients with duodenal adenocarcinoma, 7 have died, 2 have had recurrences, and 2 are disease free. Actuarial and disease-free, 2-year survival rates in the 11 patients with duodenal adenocarcinoma were 33% and 14%, respectively. CONCLUSIONS: Pancreas-sparing duodenectomy is a safe and effective treatment in patients with distal duodenal benign neoplasms or trauma, and PSD appears to have limited effectiveness for malignant distal duodenal pathology.
BACKGROUND & AIMS: Hepatitis G virus (HGV) is transmissible by blood transfusion, but its role in chronic liver disease is unknown. The aim of this study was to determine the prevalence of HGV infection in patients infected with hepatitis C virus (HCV) undergoing transplantation and evaluate the effects of HGV coinfection on the course of posttransplantation HCV infection. METHODS: One hundred twenty-four patients infected with HCV undergoing liver transplantation were studied. Serum samples were tested for HCV and HGV RNA; HCV RNA was quantitated by branched DNA assay, and HCV genotype was determined. RESULTS: The prevalence of pretransplantation and posttransplantation HGV infection was 24% and 28%, respectively. Pre-transplantation HGV infection was positively correlated with posttransplantation HGV infection (P < 0.001). Pretransplantation clinical features were not different in patients infected with HCV with and without HGV infection. Posttransplantation HCV RNA levels were not significantly different in patients with and without HGV coinfection, but HCV genotype 1b was more frequent in patients with HGV coinfection. There were no differences in the histological severity of posttransplantation liver disease, graft, and patient survival between patients with and without HGV infection. CONCLUSIONS: Although HGV coinfection is frequent in patients with end-stage HCV disease undergoing liver transplantation, there is no association between the presence of HGV coinfection and the severity of liver disease post-transplantation, graft, or patient survival.
BACKGROUND: Peripheral atherosclerosis in young adults has been associated with a high amputation rate. Our purpose was to examine the natural history of amputees with premature atherosclerosis. METHODS: We compared 50 consecutive young patients undergoing dysvascular amputation who were 49 years of age or younger (mean age +/- SEM, 43 +/- .7 years) with 75 consecutive men and women ranging in age from 60 to 75 years (mean age, 67 +/- .6 years) who were undergoing major amputations for atherosclerosis during the same period. RESULTS: Before undergoing amputation 46 (92%) patients in the study group underwent a mean of 3 +/- 0.3 vascular operations, and 49 (65%) older patients in the control group underwent a mean of 2 +/- 0.2 vascular operations (p = 0.003). The mean time from onset of symptoms to first amputation was not different in the study group versus the control group. Of those patients surviving until discharge, 20 (45%) patients in the study group and 21 (31%) patients in the control group became community or household ambulators, whereas 24 (55%) patients in the study group and 47 (69%) patients in the control group were confined to wheelchairs or were bedridden (p = 0.17). Seventeen (74%) patients in the study group who did not require contralateral amputations became community ambulators, as did 18 (38%) members of the control group (p = 0.01). Twenty (40%) patients in the study group and 39 (52%) patients in the control group died during the study period. The mean age at death was 48 +/- 1 years for the study group and 69 +/- .8 years for the control group (p < 0.001). Cumulative 5-year survival (62% patients in study group, 47% patients in control group) was not different between the two groups (p = 0.41, Kaplan-Meier). CONCLUSIONS: Compared with older counterparts, amputees with premature atherosclerosis have a higher number of failed bypasses before undergoing amputation and die at a younger age. However, both groups have a similar cumulative survival after amputation. Fewer than one half of young patients undergoing dysvascular amputation ultimately achieve ambulation, suggesting that major amputations are a harbinger of long-term disability and dependency in these patients. Because young patients had a higher potential for rehabilitation after unilateral amputation, these patients should be monitored closely for development of ischemia in the contralateral limb.
The large number of hazardous chemicals manufactured, transported, and stored in the United States creates the potential for significant toxic exposures to workers in industry today. Emergency physicians are likely to be called upon to evaluate many of these exposures when they occur in the acute setting. In addition to single-patient exposure, significant potential exists for such exposures in the setting of mass casualties. Emergency physicians need a source of readily available information regarding chemical hazards that can be helpful in the diagnosis and treatment of such exposures. The Material Safety Data Sheet (MSDS) is reviewed herein, with special attention given to the sort of information that can be found on the MSDS and how such information can be clinically helpful to emergency physicians. The significant drawbacks and limitations of MSDS documents are also reviewed.
Although older, potentially sedating, "first-generation" antihistamines (H1-receptor antagonists) are commonly used in childhood, their central nervous system (CNS) effects have not been well-documented in young subjects. We hypothesized that diphenhydramine and hydroxyzine would affect CNS function adversely in this population. Our objective was to evaluate the effects of these medications on central and peripheral histamine H1-receptors in children. Fifteen subjects with allergic rhinitis were tested before and 2-2.5 h after administration of diphenhydramine, hydroxyzine, or placebo in a double-blind, single-dose, three-way crossover study. Impairment of cognitive processing was assessed objectively by the latency of the P300 event-related potential (P300). Somnolence was assessed subjectively by a visual analog scale. Peripheral H1-blockade was assessed by suppression of the histamine-induced wheals and flares. At the central (Cz) and frontal (Fz) electrodes, diphenhydramine and hydroxyzine increased the P300 latency significantly (P < 0.05) compared to baseline. Hydroxyzine increased somnolence, as recorded on the visual analog scale, significantly compared to baseline (P < 0.05), with a similar trend for diphenhydramine (P = 0.07). Both antihistamines reduced histamine-induced wheals and flares significantly compared to baseline and compared to placebo. In children, diphenhydramine and hydroxyzine are effective H1-receptor antagonists, but both these medications cause CNS dysfunction, as evidenced by increased P300 latency, a measure of cognitive function, and by increased subjective somnolence.
Explore the source record for details and available documents.
Pseudomonas mevalonii 3-hydroxy-3-methylglutaryl-CoA lyase is affinity labeled by 2-butynoyl-CoA; peptide sequence analysis demonstrates C237 to be the site of modification [Hruz et al. (1992) Biochemistry 31, 6842-6847]. In order to evaluate whether C237 functions in the chemistry of hydroxymethylglutaryl-CoA cleavage, cassette mutagenesis has been employed to alter wild-type DNA to encode serine or alanine at residue 237. ESR measurements indicate that the purified mutant enzymes bind stoichiometric amounts of the spin-labeled substrate analog, R.CoA, which has been established as a competitive inhibitor. Binding affinities measured with C237S (Kd = 92 microM) and C237A (Kd = 97 microM) lyases are comparable to that observed with wild-type lyase. The rotational dynamics of R.CoA bound to mutant enzymes are also very similar to those for R.CoA bound to wild-type lyase. These observations suggest that the mutant enzymes are structurally intact. In view of this demonstrated structural integrity, it is significant that the VmaxS of C237A and C237S are approximately 4 x 10(4)- and approximately 725-fold lower, respectively, than the value measured for wild-type hydroxymethylglutaryl-CoA lyase. The C237S enzyme exhibits a Km = 53 microM for substrate; this value is only 2-fold higher than the Km of the wild-type enzyme. Additionally, we report that the residual activity in C237S hydroxymethylglutaryl-CoA lyase is unaffected by 2-butynoyl-CoA under conditions which support inactivation of wild-type enzyme. These results are consistent with an active site assignment to C237, confirming the prediction based on the affinity labeling/peptide mapping data.(ABSTRACT TRUNCATED AT 250 WORDS)
The role of cysteine 266 in human 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) lyase, a residue that is homologous to a cysteine mapped to the active site of prokaryotic HMG-CoA lyase by protein chemistry approaches, has been investigated by site-directed mutagenesis. Both the wild-type human enzyme and a C323S variant, in which a regulatory sulfhydryl has been eliminated without any negative effect on catalytic activity (Roberts, J. R., Narasimhan, C., Hruz, P. W., Mitchell, G. A., and Miziorko, H. M. (1994) J. Biol. Chem. 269, 17841-17846), were used as models. Mutant enzymes C266A, C266A/C323S, C266S, and C266S/C323S were overexpressed in Escherichia coli and purified to homogeneity. In all cases, kinetic characterization indicated that the Km value for HMG-CoA was not substantially different from the value measured using wild-type human lyase, suggesting that no serious structural perturbation occurs upon replacing Cys-266. A dissociable divalent cation (Mn2+ or Mg2+), which is required for activity in both native and C323S enzymes, is also an essential component for activity in each of the Cys-266 mutants. The structural integrity of the human mutants was further indicated by Mn2+ binding studies, which demonstrate similarities not only in the activator cation binding stoichiometries, but also in the KD values for Mn2+ as determined for wild-type and mutant C266A or C266S proteins. Purified C266A and C266A/C323S mutants both displayed approximately 1.3 x 10(4)-fold diminution in specific activity, while the kcat value was diminished in both C266S and C266S/C323S by approximately 9.9 x 10(2)-fold. This large diminution in catalytic efficiency in enzyme variants that display no substantial structural perturbations is in accord with an active-site assignment to Cys-266 and qualifies its sulfhydryl group for consideration as a component of the catalytic apparatus.
Explore the source record for details and available documents.
Heart transplantation has become a highly successful, life-saving treatment for a number of otherwise fatal heart diseases. A major limiting factor in the growth of transplantation surgery has been the relative lack of suitable donor organs, and the appropriate criteria for selection of donor organs have been a topic of significant interest. Despite relatively favorable survival rates in the few patients who have received organs from victims of many types of poisonings and drug overdoses, patients dying of toxicologic causes are not usually considered suitable organ donors. Some centers routinely reject such individuals. Criteria for donor selection continue to be vague, unclear, or nonexistent in regard to organ transplantation from victims of all types of poisoning and toxic exposures. Carbon monoxide (CO) is a ubiquitous poison, and although victims of CO poisoning have occasionally served as suitable organ donors, heart transplantation in this scenario is still a very rare event. We describe the successful transplantation of the heart from a CO poisoning victim--to our knowledge, only the third such transplantation. Because the emergency department is a critical site for organ procurement, emergency physicians must be aware that patients dying of CO exposure may be acceptable organ donors.
OBJECTIVE: To determine whether a certain distance measurement on the oral endotracheal tube (ETT) at the corner of the mouth could reasonably ensure proper depth of placement in critically ill patients, without the immediate need for a confirming chest x-ray (CXR). METHODS: A prospective observational cross-sectional design was used to compare ETT mark distance and radiographic location of the ETT tip. The measurement marking on the ETT at the level of the corner of the mouth was noted at the time of intubation. The relationship of the tip of the ETT to the tracheal carina on the postintubation CXR was then determined. The ETT placement was deemed correct if the tip was at least 2 cm cephalad to the carina on the CXR. RESULTS: Of 83 intubated patients assessed, 52 were men and 31 women. The mean measurement of the ETT at the corner of the mouth was 22.2 cm for the women and 23.1 cm for the men. The mean distance from the tip of the ETT to the carina was 3.45 cm for the women and 4.13 cm for the men. Seventy-five of the 83 patients (90.4%; 95% CI 81.9-95.7%) had correct ETT positions on the initial CXR. If the ETT position had been adjusted at the corner of the mouth to 21 cm for the women and 23 cm for the men, the ETT would have been in correct position for 81 of the 83 patients (97.6%; 95% CI 89.6-95.7%). This represents a significant improvement in tube placement (p < 0.025; the McNemar chi-square). CONCLUSION: Proper depth of ETT placement in the critically ill adult patient can be estimated by the technique of this study. In this adult patient population, corner-of-the-mouth placement of the ETT using the 21-cm tube mark for the women and the 23-cm mark for the men would have led to proper placement for most patients.
Endogenous digoxin-like immunoreactive substances (DLIS) are produced by the human body and can be significantly elevated in specific clinical conditions. Commercially available digoxin assays do not have the specificity to fully distinguish DLIS from exogenous digoxin, though DLIS do not possess the same therapeutic properties as do the drug. The resultant artificial elevation of a reported digoxin level or a completely factitious level in a patient not taking the drug can have clinically significant consequences.
BACKGROUND: Children with allergic rhinitis may have difficulty with self-assessment of nasal symptoms. OBJECTIVE: To correlate objective and subjective assessments of nasal stuffiness in children with seasonal allergic rhinitis. METHODS: Children, aged 6 to 12 years, with seasonal allergic rhinitis recorded their degree of nasal obstruction on two separate occasions using a nasal stuffiness score and a visual analogue scale. Physicians also assessed the degree of nasal obstruction using a visual analogue scale. Anterior rhinometry was performed and saccharin transient time was also measured. Correlations between subjective scores and objective measurements were calculated using Spearman correlation coefficients. RESULTS: Patient's nasal stuffiness scores correlated with their visual analogue assessment (r = .45, P = .0001). Patients visual analogue assessments did not correlate with anterior nasal airflow (r = -.12, P > .05). Physicians' visual analogue assessment correlated better with nasal airflow than childrens' assessment (r = -.41, P = .0001). Saccharin transit time was not helpful in assessment of degree of nasal obstruction. CONCLUSION: Children appear to have difficulty in self-assessment of nasal symptoms, and to be poor judges of the presence or severity of nasal obstruction. In studies of allergic rhinitis in children, objective measurements should be performed, if possible, to facilitate more accurate interpretation of data.
cDNA encoding the mature form of human hydroxy-methylglutaryl-CoA (HMG-CoA) lyase, a mitochondrial matrix protein, has been used to prepare expression plasmids appropriate for production of this protein in Escherichia coli. Using a T7 RNA polymerase-based pET system, HMG-CoA lyase was overexpressed but largely recovered in an insoluble, catalytically inactive form. In contrast, an expression plasmid (pTrcHL-1), derived from pTrc99a, supported production of soluble, active enzyme. A synthetic oligonucleotide cassette was employed to produce an enzyme variant in which cysteine was replaced by serine at position 323. Both wild-type and C323S HMG-CoA lyases were isolated in homogeneous form and characterized. The function of Cys-323 in influencing catalytic activity in vitro has been investigated by comparing the response of wild-type and C323S lyases to oxidation and reduction. Additionally, the consequences of treatment of these enzymes with the sulfhydryl-directed bifunctional reagent, o-phenylenedimaleimide have been determined. The results support the hypothesis that a thiol/disulfide exchange mechanism affects enzyme activity in vitro and indicate that Cys-323 residues on adjacent subunits of the homodimeric native enzyme are suitably positioned to form an intersubunit cross-link upon oxidative inactivation and disulfide formation.
The motor effects of the partial dopamine agonist (-)-3-(3-hydroxyphenyl)-N-n-propylpiperidine [(-)-3-PPP, preclamol] were evaluated in nine patients with Parkinson's disease using a double-blind, placebo-controlled design. (-)-3-PPP monotherapy had an antiparkinsonian effect in five of nine patients at a mean dose of 37 +/- 10 mg intramuscularly. The co-administration of (-)-3-PPP and a mildly dyskinetic dose of levodopa, infused intravenously at steady-state, resulted in complete suppression of dyskinesias and reemergence of parkinsonian signs in two of seven patients. These dopamine antagonist effects of (-)-3-PPP occurred at relatively low (2.5 and 5 mg) doses. Our results suggest that partial dopamine agonists can exert agonist or antagonist activity in parkinsonian patients depending on concurrent dopaminergic tone. Although this dual action of (-)-3-PPP and other partial agonists could be therapeutically important on theoretical grounds, the small number of patients manifesting a clinically significant response and the frequently inconsistent effects could indicate that this class of agents may have relatively limited clinical utility.
Eikenella corrodens, a fastidious, slow-growing, gram-negative, facultative anaerobic bacillus may be encountered in wounds exposed to human saliva, especially human bites and head and neck infections. An unusual case of a mixed flora E corrodens and Streptococcus septic arthritis with adjacent osteomyelitis secondary to saliva contamination from licking an intravenous (i.v.) needle is presented. A literature search showed 53 previous cases of E corrodens infections in i.v. drug users. However, none of these infections affected bones or joints. The microbiology and unusual antibiotic sensitivity are presented. Recommendations for treatment include penicillin or ampicillin. Tetracycline is recommended in the penicillin-allergic patient. This is the first case that draws attention to the connection between E corrodens, i.v. drug use, and septic arthritis and osteomyelitis.