Insertion and orientation of a synthetic peptide representing the C-terminus of the A1 domain of Shiga toxin into phospholipid membranes

Shiga toxin is a bacterial protein composed of one A and five B subunits. Its A chain possesses a protease sensitive loop (Cys-242-Cys-261) that is cleaved to produce an enzymatically active A1 domain and an A2 fragment associated with its B subunit pentamer. The proposed mode of action of the toxin is linked to its retrograde transport to the ER lumen followed by the translocation of its catalytic A1 chain to the cytoplasmic side of the ER membrane. A signal sequence-like domain (residues 220-246) which constitutes the C-terminus of the A1 chain precedes a region within the protease sensitive loop (residues 247-258) that contains known and putative cleavage sites. Two peptides corresponding to this C-terminus (residues 220-246) were chemically synthesized to investigate if this signal sequence-like domain can interact with membranes. Such a property may provide a clue to the mechanism of translocation of the A1 domain across the ER membrane. The first peptide represented the native sequence, which includes a naturally occurring cysteine at position 242 and provided a thiol moiety for the attachment of a spinlabel. A second peptide was designed to contain a single tryptophan residue (Ile232Trp) located within the hydrophobic core of the sequence which served as an intrinsic fluorescence probe. The interactions of both peptides with lipid vesicles were analyzed by circular dichroism, fluorescence, and EPR spectroscopy. The peptides lack structure in aqueous buffers and adopted an alpha-helical geometry when bound to negatively charged lipid vesicles. The addition of lipid vesicles to a solution of the tryptophan-containing peptide results in a blue shift in the wavelength of its fluorescence maxima as well as an increase in fluorescence intensity at 335 nm, suggesting that the hydrophobic core of this A1 peptide relocated to a nonpolar environment. EPR measurements of a proxyl-labeled analog of the peptide (introduced at Cys-242) indicated a decreased mobility of a fraction of the proxyl probe in the presence of lipid vesicles. At pH 7, the membrane-bound probe was completely reduced by ascorbate trapped inside vesicles but only partially reduced by ascorbate added outside the vesicles, suggesting that the C-terminal region of the peptide traversed the membrane bilayer or relocated close to the surface of its inner lipid leaflet. Finally, the peptide was shown to insert into lipid vesicles, causing the release of calcein at a high peptide:lipid ratio. These results suggest that the C-terminal tail of the A1 chain may anchor this domain into the ER membrane.

Plasma exchange therapy for solar urticaria

We report two cases of severe idiopathic solar urticaria treated with plasma exchange therapy. Previous treatment which included antihistamines and, in one patient, desensitization with psoralens and ultraviolet A (PUVA) and narrowband ultraviolet B phototherapy produced only partial benefit. The effect of plasma exchange therapy was assessed using monochromator phototesting and intradermal injection of in vitro irradiated serum. One patient responded but relapsed within 2 weeks. We have failed to demonstrate a lasting benefit from plasma exchange therapy (PExT) in the treatment of two patients with idiopathic solar urticaria.

Myocardial infarction patients in the 1990s--their risk factors, stratification and survival in Canada: the Canadian Assessment of Myocardial Infarction (CAMI) Study

OBJECTIVES

This study sought to evaluate the in-hospital and postdischarge mortality of patients with an acute myocardial infarction in the 1990s.

BACKGROUND

The widespread implementation of therapeutic interventions that modify the natural history of coronary artery disease has led to changes in the profile and survival of patients with an acute myocardial infarction. Although data exist for selected subsets of patients with an acute myocardial infarction, at this time there is little recent prospective information on all patients presenting with an acute myocardial infarction, particularly for survival after hospital discharge.

METHODS

All patients < or = 75 years old presenting with an acute myocardial infarction between July 1, 1990 and June 30, 1992 at nine Canadian hospitals were prospectively evaluated and followed up for 1 year. From November 1991, patients of all ages were included. In two centers, recruitment continued until December 31, 1992. A total of 3,178 patients were recruited.

RESULTS

The in-hospital mortality rate of patients < or = 75 years old was 8.4%, and that at 1 year after hospital discharge was 5.3%. For patients of all ages recruited after November 1, 1991, the in-hospital mortality rate was 9.9% and 7.1% for 1 year after hospital discharge. For patients < or = 75 years old, age carried an independent in-hospital but no post discharge risk. Female patients had a twofold greater risk of dying in hospital. After hospital discharge, only 1.7% of patients < or = 75 years old and 1.9% of patients of all ages died of a presumed arrhythmic death. Premature ventricular contractions had no independent prognostic value. The relatively low in-hospital (5.3%) and postdischarge (6.1%) reinfarction rate may have contributed to improved survival. A greater reinfarction rate in patients >75 years old (17.4% vs. 9.6%, p < 0.001) may have contributed to their poorer outcome.

CONCLUSIONS

One-year mortality after acute myocardial infarction continues to decrease, and changes in the prognostic value of traditional methods of risk stratification have occurred.

Pharmacodynamics of torsemide administered as an intravenous injection and as a continuous infusion to patients with congestive heart failure

The natriuretic and diuretic effects of a 100-mg dose of torsemide administered as a continuous infusion of torsemide and as a single bolus were compared in a group of patients with stable mild-to-moderate congestive heart failure (CHF). Patients received in random order 100 mg of torsemide as an intravenous bolus and as a 75-mg infusion over 24 hours started simultaneously with a 25-mg loading bolus. Administration of torsemide to patients with CHF as a continuous infusion was an effective dosing regimen, resulting in 24-hour diuresis and natriuresis that was numerically but not statistically greater than that observed with bolus administration. The response with continuous infusion occurred with less torsemide in the urine, resulting in a significantly greater efficiency of torsemide with this regimen. The effectiveness of torsemide as a continuous infusion does not mean that this mode of administration should be used in all patients. The response to 100 mg of torsemide in patients with mild-to-moderate CHF is the same whether administered as an intravenous bolus, a continuous intravenous infusion, or by mouth. This is consistent with the high bioavailability demonstrated in previous studies. The mode of therapy used should be dictated by each individual patient's needs. This study shows that continuous infusion is a viable option for administration of torsemide, and dosing guidelines for use of such a strategy are presented.

Hepatitis C virus: epidemiology and genotypes in the north east of England

The epidemiology of hepatitis C virus (HCV) infection was studied in an English teaching hospital over an 18 month period. A total of 104 HCV antibody positive patients were referred for further investigation. They were divided into those diagnosed through screening (blood donors and intravenous drug abusers) and those diagnosed for other reasons, and their mean ages, known risk factors for HCV transmission, genotypes, and liver biopsy histology were analysed. Screened patients were significantly younger than the others. No significant difference in age was found between genotypes. Most patients genotyped (69%) were genotype 1. Intravenous drug abusers had a higher proportion of subtype 1a, and patients who acquired HCV through blood transfusion had a higher proportion of subtype 1b. Liver biopsy specimens were scored using a histological activity index for liver inflammation and fibrosis. Patients with subtype 1b had significantly more severe liver disease than other genotypes when the histological activity index scores for fibrosis were analysed (p < 0.05). Liver disease worsened significantly with age according to all three histological activity index scores (portal activity: p < 0.01, acinar activity: p < 0.001, fibrosis: p < 0.0001). Liver disease worsened with increased duration of infection (p < 0.002), and patients who also abused alcohol presented at a significantly younger age (cirrhosis, p < 0.05, hepatocellular carcinoma, p < 0.02).

Clinically suspected scaphoid fracture: a comparison of magnetic resonance imaging and bone scintigraphy

59 patients with clinical suspicion of scaphoid fracture, but negative radiographs at presentation and review, were examined by magnetic resonance imaging (MRI) and bone scintigraphy (BS). The diagnoses were compared with subsequent follow-up. There were four scaphoid fractures, 10 other fractures and three significant ligamentous injuries. All scaphoid fractures were identified by MRI and BS. MRI showed better interobserver agreement for scaphoid injury than BS and fewer false positive reports. Significant ligamentous injury and carpal instability diagnosed by MRI were not evident on scintigraphy. Using fast scanning protocols, the cost of MRI is comparable with that of BS. MRI should be considered as the appropriate second line investigation in these clinical circumstances.

Effects of rating parameters on assessment of neuroleptic-induced vacuous chewing movements

Long-term administration of neuroleptics to rats produces a syndrome of vacuous chewing movements (VCMs). The validity of the VCM syndrome as a model for tardive dyskinesia (TD) in humans is unclear. This is due, in part, to inconsistencies between studies. Methods for rating VCMs have varied markedly and could account for the inconsistencies. The purpose of this study was to evaluate the importance of the different methods on VCM scores. The effects of habituation and length of rating sessions were examined in rats habituated for 2 min, 1 h, or several hours over 4 days, compared to unhabituated rats. Ratings with and without habituation were highly correlated, as were ratings from 2- and 5-min observation periods. Ratings from neuroleptic-treated rats in restraining tubes, however, were significantly correlated with unrestrained ratings only following several hours of habituation. Locomotor activity was not correlated with VCM scores. These results suggest that habituation to open cages is not an important factor in assessing VCMs. Use of restraining tubes, however, may alter scores. The lack of an habituation effect or of a relationship between activity and VCMs suggests that locomotor and oral behaviors are not necessarily in competition. Restraining rats to rate VCMs does not appear to be necessary and could alter the neurobiology of VCMs.

Cloning and characterization of the Streptomyces peucetius dnrQS genes encoding a daunosamine biosynthesis enzyme and a glycosyl transferase involved in daunorubicin biosynthesis

The dnrQS genes from the daunorubicin producer Streptomyces peucetius were characterized by DNA sequencing, complementation analysis, and gene disruption. The dnrQ gene is required for daunosamine biosynthesis, and dnrS appears to encode a glycosyltransferase for the addition of the 2,3,6-trideoxy-3-aminohexose, daunosamine, to epsilon-rhodomycinone.

The development of a post-operative pain service (1): An overview

Slapping the patient on the face and saying: "It's all over" is a complete inversion of the truth. As far as the patient is concerned, it is just the beginning. This patient's view is supported by the report of a Working Party on Pain after Surgery which concluded that "the treatment of pain after surgery in British hospitals is inadequate and has not advanced significantly for many years". Yet failure to relieve pain is unacceptable not only for humanitarian reasons but also because unrelieved pain may inhibit optimal recovery. In their recommendations the Working Party placed a high priority on the establishment of an acute pain team in all acute general hospitals. This team would be responsible for education, research, audit, promoting pain assessment and ensuring adequate resources and safe practice.

Follow up of an immunocompromised contact group of a case of open pulmonary tuberculosis on a renal unit

BACKGROUND

The organisation, management, outcome and cost of follow up of a large group of mainly immunocompromised patients and healthcare workers who were exposed to a staff member of a London renal unit with smear positive pulmonary tuberculosis are described.

METHODS

Following British Thoracic Society (BTS) guidelines, 576 close contacts were identified and divided into three groups: (1) 303 renal patients including 61 with renal transplants; (2) 90 surgical patients; and (3) 183 staff members. Screened contacts were interviewed, completed a symptoms questionnaire, and were offered a chest radiograph and Heaf or Mantoux test if appropriate with referral to a chest physician if required.

RESULTS

Overall, 524 (85%) living contacts have been screened: 243 (97%) renal (first screening), 63 (70%) surgical, and 135 (74%) staff contacts. Thirty one transplant patients were prescribed isoniazid chemoprophylaxis. Fifty two renal patients had died before screening and 11 deaths occurred after first interview. One case of tuberculosis epidemiologically related to the index case was diagnosed on clinical criteria. A review of the case records and/or death certificates and entries on to tuberculosis registers indicated no further cases. The cost of the investigation was estimated to be approximately franc25 000, or franc44 per contact screened, with staff costs comprising 79% of the total.

CONCLUSIONS

Undiagnosed tuberculosis in healthcare workers working with immunosuppressed patients can lead to large and expensive follow up studies. The applicability of the 1990 and 1994 BTS guidelines to the investigation of tuberculosis in an immunocompromised nosocomial group, and the role of the infection control doctor and the consultant in Communicable Disease Control in overlapping nosocomial and community incidents, are discussed.

Narrow-band UVB (TL-01) phototherapy: an effective preventative treatment for the photodermatoses

Twenty patients with photodermatoses [actinic prurigo (n = 6), hydroa vacciniforme (n = 4), idiopathic solar urticaria (n = 1), amiodarone-induced photosensitivity (n = 1) and a range of cutaneous porphyrias (n = 8)] were treated with a 'hardening' course of narrow-band ultraviolet B (TL-01) phototherapy in springtime. The response to phototherapy was monitored subjectively, by interviewing patients after the summer, and objectively by monochromator phototesting, before and after phototherapy. Fifteen patients reported that treatment was worthwhile. Monochromator phototesting after phototherapy revealed a fourfold increase in the minimal erythema dose in those with abnormal photosensitivity to ultraviolet A wavebands. Adverse effects included erythema (seven patients), pruritus (five) and provocation of the eruption (four). We now routinely consider narrow-band UVB phototherapy for problem photodermatoses.

Phase I evaluation of therapy with four schedules of 5-fluorouracil by continuous infusion combined with recombinant interferon alpha

The purpose of this study was to determine the maximum tolerated dose and dose-limiting toxicities of 5-fluorouracil (5-FU) when administered concurrently with recombinant IFN-alpha using four continuous infusion (CI) dosing schedules of 5-FU. Forty-five patients with advanced or refractory cancers were treated with 5-FU by CI, plus IFN during the infusion only, by one of four schedules: schedule A: 24-h 5-FU infusion repeated weekly, 9 x 10(6) units IFN x 2 doses weekly; schedule B: 48-h 5-FU infusion repeated weekly, 9 x 10(6) units IFN x 4 doses weekly; schedule C: 5-day 5-FU infusion repeated every 3 weeks, 9 x 10(6) units IFN three times weekly; and schedule D: 21-day 5-FU infusion, repeated after 7 days off therapy, 9 x 10(6) units IFN three times weekly. At least three patients were treated at all dose levels. Doses of 5-FU were escalated to the next level if less than one half of the patients at a given level developed grades 2-4 toxicity. The maximum tolerated dose for 5-FU was 2150 mg/m2/week for schedule A (24-h CI), 2350 mg/m2/week for schedule B (48-h CI), 750 mg/m2/day for schedule C (5-day CI), and 175 mg/m2/day for schedule D (21-day CI). Median delivered dose intensities at these levels were 1788 mg/m2/week for schedule A, 2192 mg/m2/week for schedule B, 1250 mg/m2/week for schedule C, and 593 mg/m2/week for schedule D. The dose-limiting toxicities were hematological and gastrointestinal (stomatitis, diarrhea, nausea, anorexia) for schedules A and B and gastrointestinal (mostly stomatitis) for schedules C and D. Severe fatigue due to IFN was rare. Responses correlated with toxicity >/= grade 2, but not with increased dose intensity. Responses were noted in several tumor types on schedules A, B, and D. 5-FU can be combined with IFN using 24- and 48-h high-dose and long-term low-dose CI schedules, with large differences in dose intensity at maximum tolerated dose. Shorter infusions produce less mucosal and more hematological toxicity. Tumor responses were seen on both short- and long-term CI schedules. Future studies can establish the efficacies of these new schedules of 5-FU/IFN administration in specific tumor types.

Evaluation of a new, semiquantitative screening culture device for urine specimens

The EZ Streak urine culture device (Difco Laboratories, Detroit, Mich.) combines the advantages of both the dip-slide and the classic urine culture technique, enabling bacterial enumeration and isolation following a simple inoculation step. Five hundred clean-catch urine specimens submitted by outpatients attending a health maintenance organization were used to compare the EZ Streak with culture using a 0.001-ml loop. Complete agreement of colony counts determined by the two methods was obtained for 114 (91.2%) of 125 positive specimens, but 99.2% of the results agreed in clinical interpretation, indicating the presence or absence of bacteriuria. Overall agreement between the EZ Streak and culture was 95.7%. The sensitivity and specificity of the EZ Streak were determined to be 98.4 and 99.4%, respectively. For this patient population, the EZ Streak was determined to be a reliable replacement for routine urine culture.

The diagnostic implication of falcine calcification on plain skull radiographs of patients with basal cell naevus syndrome and the incidence of falcine calcification in their relatives and two control groups

The purpose of our study was to identify the incidence of falcine calcification shown on plain skull radiographs in people with basal cell naevus syndrome (BCNS) and in their relatives compared with a normal population. A population of people with BCNS and their relatives was identified on non-radiological grounds and the incidence of falcine calcification on skull radiographs in each of these two groups was compared with the incidence of falcine calcification in a control group of people and of a larger group who attended casualty departments. Falcine calcification was graded into dense, fine but definite, and faint. 85 people with BCNS had nearly 100% incidence of falcine calcification in adults. 83 first degree unaffected relatives showed no excess over "normal" incidence of falcine calcification. In the 970 casualty patients some falcine calcification was common (> 20%) in males over 30 and in females over 50 years of age. It occurred earlier and was more common in males than in females. Dense calcification occurred in 5-7% of females and males over 60 years of age. Dense calcification was rare (< 2%) under the age of 40 years. In conclusion, falcine calcification should be regarded as the fourth major feature and a very important diagnostic feature of BCNS. An adult labelled as a BCNS sufferer without falcine calcification probably has not got the syndrome. The genetic defect responsible for the metabolic defect resulting in dural calcification is probably the same as, or in close linkage disequilibrium to, that responsible for the major clinical features of the syndrome. The age and sex distribution of falcine calcification in a general hospital casualty population is described.

Loligomers: design of de novo peptide-based intracellular vehicles

Defined branched peptides (loligomers) incorporating cytoplasmic translocation signals, nuclear localization sequences, and fluorescent probes were designed and synthesized to demonstrate the feasibility and simplicity of creating novel classes of intracellular vehicles. Loligomers containing all the above signals were rapidly internalized by Chinese hamster ovary (CHO) cells and accumulated in their nucleus. At 4 degrees C, the interaction of peptide constructs with CHO cells was limited to membrane association. Loligomers entered cells at higher temperatures by adsorptive endocytosis. Inhibitors of ATP synthesis affected cytoplasmic import only weakly but abolished nuclear uptake. The peptide signals guided both cytoplasmic and nuclear localization events. The properties exhibited by loligomers suggest a strategy for the facile design of "guided" classes of intracellular agents.

The phototumorigenic potential of broad-band (270-350 nm) and narrow-band (311-313 nm) phototherapy sources cannot be predicted by their edematogenic potential in hairless mouse skin

The new Philips TL01 narrow-band (311-313 nm) and conventional broad-band (e.g., Philips TL12; 270-350 nm) sources are effective for psoriasis phototherapy, for which treatment regimens are based on a predetermined minimal erythema dose. TL01 phototherapy treatment times are approximately half those with TL12 for psoriasis, whereas the cumulative exposure doses at clearing are similar. We compared the phototumorigenic potential of TL01 and TL12 radiation in mouse skin. Groups of albino Skh-1 hairless mice were exposed for 5 d/week at three dose levels. At each dose level, TL12 and TL01 doses were equally edematogenic. At each dose level, TL01 radiation was significantly more effective at producing first tumors of 1 mm in diameter and multiple tumors. At the lower two dose levels, TL01 radiation produced a significantly greater proportion of squamous cell carcinomas. This study demonstrates that TL01 radiation is more phototumorigenic than TL12 radiation at equally edematogenically weighted doses. This is in contrast with previous reports that edema production by polychromatic sources is predictive of their phototumorigenic effect in Skh-1 mice. The absolute cumulative TL12 dose needed to induce tumors was much less than that for TL01 radiation. The possibility of increased tumor risk with TL01 phototherapy should be considered but must be balanced against the high phototherapeutic efficacy of this source, short treatment times, and the low cumulative doses necessary for clearing of psoriasis.

Regulation of daunorubicin production in Streptomyces peucetius by the dnrR2 locus

Sequence analysis of the dnrR2 locus from the cluster of daunorubicin biosynthesis genes in Streptomyces peucetius ATCC 29050 has revealed the presence of two divergently transcribed open reading frames, dnrN and dnrO. The dnrN gene appears to encode a response regulator protein on the basis of conservation of the deduced amino acid sequence relative to those of known response regulators and the properties of the dnrN::aphII mutant. Surprisingly, amino acid substitutions (glutamate and asparagine) at the putative site of phosphorylation (aspartate 55) resulted in a reduction rather than a complete loss of DnrN activity. The deduced DnrO protein was found to be similar to the Streptomyces glaucescens tetracenomycin C resistance gene repressor (TcmR) and to two Escherichia coli repressors, the biotin operon repressor (BirA) and the tetracycline resistance gene repressor (TetR). The dnrN::aphII mutation was suppressed by introduction of the dnrI gene on a plasmid. Since the introduction of dnrN failed to restore antibiotic production to a dnrI::aphII mutant, these data suggest the presence of a regulatory cascade in which dnrN activates the transcription of dnrI, which in turn activates transcription of the daunorubicin biosynthesis genes.

Methods to assess RAST results in patients exposed to chemical allergens

RAST is routinely used to assess the presence of IgE antibodies against environmental allergens in the sera of symptomatic patients. With exposure to low-mol.-mass (chemical) allergens, RAST is also done, but the interpretation of results is more difficult. A study was undertaken to assess methods which have been employed to determine the positivity of sera and to develop an objective, statistically based procedure for determination of RAST positivity to chemical allergens. Sera were obtained from 14 nonsensitized (control) subjects and examined for total IgE by radioimmunoassay, and for cyanuric chloride (CyCl)-specific IgE by RAST. Linear regression analysis revealed the correlation between the tests to be 0.94. Equations for the 95% and 99% predicted intervals were obtained. Sera from 19 cyanuric chloride workers were tested for total and specific IgE. Positivity of RAST results was determined by three methods: RAST inhibition, RAST ratio (binding to CyCl-human serum albumin (HSA) disks/HSA disks), and the regression equation where values outside the 99% predicted interval were considered to be positive and those > 95% < 99% were considered to be borderline values. Determination of CyCl RAST positivity by the regression method gave results comparable to those obtained from RAST inhibition, whereas the RAST ratio resulted in many more false positive conclusions. This statistical approach to RAST analysis was also used to assess sera from patients exposed to the unrelated chemical allergens, toluene diisocyanate and formaldehyde. Conclusions based on the regression method were in good agreement with those from RAST inhibition assay. Moreover, use of one standard curve may be sufficient for interpretation of RAST results for diverse haptenic allergens. These results indicate that the regression method provides a statistical basis from which to determine positivity of RAST analyses while eliminating the need for RAST inhibition assays.