Distinction between immunogenicity and tolerogenicity among HBcAg T cell determinants. Influence of peptide-MHC interaction

One purpose of this study was to examine the concept of T cell immunodominance employing a neonatal tolerance model. The extent to which a single T cell recognition site can represent the total T cell response to hepatitis B core Ag (HBcAg) was examined in the B10.S and B10 murine strains. It was shown that the entire B10.S T cell response to HBcAg was focused on a single immunodominant site represented by residues 120-131. This was demonstrated by exposing B10.S neonatal mice to p120-140 or p120-131, which resulted in a state of T cell tolerance to the entire HBcAg. In contrast, p120-140 contained an immunogenic T cell site for B10 mice, p129-140, but this site was nontolerogenic. Similarly, injection of p120-140 into (B10.S X B10)F1 neonatal mice resulted in tolerization of p120-131-specific, I-As-restricted T cells, but not of p129-140-specific, I-Ab-restricted T cells. The second purpose of this study was to attempt to explain the immunologic basis of an immunogenic yet nontolerogenic T cell determinant. It was shown that the p120-131 T cell site, which is immunogenic and tolerogenic in B10.S mice, could be converted into an immunogenic/nontolerogenic T cell site by a single amino acid substitution in either residue 127 or 129. Residues 127 and 129 were previously shown to be involved in interaction with MHC class II molecules (agretopic). These results demonstrated that the relative avidity of a peptide-MHC interaction can influence T cell tolerance induction. Furthermore, the results suggest that a higher threshold of peptide-MHC avidity may be required to induce T cell tolerance as compared to the threshold of peptide-MHC avidity required to immunize T cells.

Functional identification of agretopic and epitopic residues within an HBcAg T cell determinant

Residues 120-131 within the hepatitis B core Ag (HBcAg) represent a dominant T cell recognition site for mice of the H-2S haplotype. This study was undertaken in order to identify residues within the p120-131 sequence which either interact with the TCR termed epitopic residues or interact with MHC class II molecules termed agretopic residues. For this purpose a panel of analogs of p120-131 composed of peptides containing single alanine substitutions for each residue was synthesized. These peptides were analyzed functionally for their ability to stimulate p120-131 or HBcAg-primed T cells and for their immunogenicity in B10.S or [B10.S X B10 (nonresponder)]F1 mice. Furthermore, analogs of p120-131 were used as stimulators and inhibitors of T cell activation in competitive inhibition experiments. Cumulatively these functional studies allowed us to identify residue 125 as a dominant epitopic residue and residues 127 and 129 as dominant agretopic residues. Furthermore, a p120-131 analog containing an alanine substitution for the dominant agretopic residue was immunogenic in B10.S mice, but was nonimmunogenic in (B10.S X B10)F1 mice indicating that T cell responsiveness is influenced by MHC class II gene dosage effects and can be inherited in an apparent recessive manner. In this study, critical residues involved in the immunogenicity of this dominant T cell determinant of HBcAg were defined, in a companion study, the influence of these residues on tolerogenicity was examined.

Distinction between immunogenicity and tolerogenicity among HBcAg T cell determinants. Influence of peptide-MHC interaction

One purpose of this study was to examine the concept of T cell immunodominance employing a neonatal tolerance model. The extent to which a single T cell recognition site can represent the total T cell response to hepatitis B core Ag (HBcAg) was examined in the B10.S and B10 murine strains. It was shown that the entire B10.S T cell response to HBcAg was focused on a single immunodominant site represented by residues 120-131. This was demonstrated by exposing B10.S neonatal mice to p120-140 or p120-131, which resulted in a state of T cell tolerance to the entire HBcAg. In contrast, p120-140 contained an immunogenic T cell site for B10 mice, p129-140, but this site was nontolerogenic. Similarly, injection of p120-140 into (B10.S X B10)F1 neonatal mice resulted in tolerization of p120-131-specific, I-As-restricted T cells, but not of p129-140-specific, I-Ab-restricted T cells. The second purpose of this study was to attempt to explain the immunologic basis of an immunogenic yet nontolerogenic T cell determinant. It was shown that the p120-131 T cell site, which is immunogenic and tolerogenic in B10.S mice, could be converted into an immunogenic/nontolerogenic T cell site by a single amino acid substitution in either residue 127 or 129. Residues 127 and 129 were previously shown to be involved in interaction with MHC class II molecules (agretopic). These results demonstrated that the relative avidity of a peptide-MHC interaction can influence T cell tolerance induction. Furthermore, the results suggest that a higher threshold of peptide-MHC avidity may be required to induce T cell tolerance as compared to the threshold of peptide-MHC avidity required to immunize T cells.

External fixation of femoral fractures. Indications and limitations

The role of external fixation in the management of femoral shaft fractures is reviewed based on a study of 24 femoral fractures managed by either an AO or a Wagner external fixator during 1983-1986. Indications included open fractures with soft-tissue injury (13 patients), comminuted shaft fractures (six patients), and unstable operative candidates (five patients). In 14 patients, external fixation was a temporary method (Group I), while in ten patients it was the definitive method of stabilization (Group II). Twenty-one patients achieved solid union, two developed a delayed union, and one had a nonunion. Three patients developed pin-tract infections, and one developed osteomyelitis after intramedullary fixation in Group I. Two patients in Group II developed shortening (2.1 cm and 3.2 cm). Loss of motion occurred in 11 patients, averaging 56 degrees. It is suggested that external fixation be considered in the following types of femoral fractures: open fractures for aggressive management of soft-tissue injuries; closed fractures in severely traumatized, burn, or head injury patients; fractures about the knee resulting in floating knees; and infected femoral nonunions and pseudarthroses.

Retroviral-mediated transfer and expression of hepatitis B e antigen in human primary skin fibroblasts and Epstein-Barr virus-transformed B lymphocytes

Previously, an amphotropic retroviral expression system coding for the neomycin resistance gene was developed and used to synthesize hepatitis B e antigen (HBeAg) and hepatitis B core/e antigen (HBc/eAg) in transfected mouse NIH 3T3 fibroblasts (A. McLachlan et al., 1987, J. Virol. 61, 683-692). In the present study, these transfected cell lines were infected with a helper amphotropic murine leukemia virus resulting in the production of infectious recombinant retrovirus. The recombinant retrovirus was examined for its capacity to transmit resistance to the antibiotic, G418, and to express hepatitis B virus antigens in mouse NIH 3T3 fibroblasts, human primary skin fibroblasts, and Epstein-Barr virus (EBV)-transformed B lymphocytes. A mouse NIH 3T3 fibroblast clone was generated which produced recombinant retrovirus with the capacity to transmit HBeAg expression to these murine and human cell lines. In contrast, it was not possible to transmit HBc/eAg synthesis efficiently to these cell lines by recombinant retroviral infection. The difference between the efficiencies of transmission of HBeAg and HBc/eAg expression by recombinant retroviral-mediated infection was not predicted as the expression vector coding for HBc/eAg synthesis differs only by the deletion of approximately 90 nucleotides of HBV DNA sequence from the vector coding for HBeAg synthesis.

Metallurgical evaluation of retrieved implants and correlation of failures to patient record data

This study sought to establish an orthopedic implant retrieval program according to ASTM F561-87 (the American Society for Testing and Materials) and to describe the results of evaluation of failed implants. A total of 275 fracture fixation and prosthetic devices have been retrieved to date. Results of metallurgical evaluation showed no deviations in ASTM specifications among the failed implants evaluated. The cause of failure in most cases was fatigue following nonunion or delay in healing.

Tire explosion injuries

Twenty-five patients hospitalized with injuries sustained from tire explosions from 1980 to 1987 were reviewed. Injuries occurred directly from the tire rim or parts of its assembly, from the patient being thrown against adjacent unyielding structures, or a combination of these. Lethal or life-threatening injuries do occur, so these patients initially must be triaged as polytrauma patients. Resuscitation and expeditious attention to life-threatening injuries must be provided when necessary. Serious head, facial, eye, and upper extremity injuries occurred frequently. Pelvic and long-bone fractures, particularly those of the femur, are stabilized primarily as part of the overall treatment of the polytraumatized patient. Open fractures and fractures with arterial injuries and/or compartment syndromes are primarily decompressed, debrided, and appropriately stabilized. After life-threatening and limb-threatening injuries are attended, eye injuries that threaten sight should be addressed. While hand, wrist, and other upper extremity injuries that do not fall in the above categories may not require immediate or primary treatment, they are often critical in determining the patient's final outcome. This is particularly true since most patients are manual workers, often mechanics. Therefore, hand, wrist, and upper extremity injuries should be treated as early as possible and in parallel with other injuries to achieve optimal results and minimize impairment, disability, and time and economic loss from work. Strong emphasis should be placed on education and safety training in preventing this severe form of civilian trauma.(ABSTRACT TRUNCATED AT 250 WORDS)

Post-embedding methods for immunolocalization of elastin and related components in tissues

Elastic tissue is composed of amorphous-appearing elastin and 12-nm diameter microfibrils, one component of which has recently been isolated and characterized as the 31 KD microfibril-associated glycoprotein MAGP. Monospecific antibodies to each of these components have been developed in this laboratory. The parameters that determine optimal localization of colloidal gold probes for post-embedding immunolabeling of elastic tissue components have been systematically studied in a variety of normal and developing tissues in mammals and birds. Protein A-gold probes stabilized with dextran have been shown to provide complexes that remain stable after more than 2 years. Conditions have been defined that permit precise localization within the extracellular matrix of antibodies to MAGP and to elastin, singly and together. Best results were obtained with acrylic resins (Lowicryl K4M or LR White). Fixation in glutaraldehyde or other aldehydic fixatives, with or without osmium, did not affect the immunostaining of elastic tissue with affinity-purified antibodies to tropoelastin, or to anti-[alpha-elastin] or anti-[alkali-insoluble elastin]. Immunostaining with the anti-MAGP antibody was less robust and was possible in tissues which had been fixed only lightly before embedding in Lowicryl K4M or LR White. This staining was enhanced by metaperiodate oxidation of the sections as well as by reduction of the tissues with sodium borohydride en bloc, followed by hyaluronidase digestion of the sections. The effects on immunostaining of a range of enzyme digestions have also been examined. Conditions have thus been defined that make possible detailed study of the relationship between elastic tissue, elastin-associated microfibrils, and other microfibrillar structures in normal and abnormal tissues during development and aging.

Comparative immunogenicity of hepatitis B virus core and E antigens

The nucleocapsid (hepatitis B core Ag (HBcAg] of the hepatitis B virus is a particulate Ag composed of a single polypeptide (p21). Although a non-particulate form of HBcAg designated hepatitis B e Ag (HBeAg) shares significant amino acid identity, the immune responses to these Ag appear to be regulated independently. This report describes the use of recombinant HBcAg and HBeAg to examine and compare murine T cell and B cell recognition of these related Ag. The HBcAg preparation was stable at pH 7.2 and 9.6 and expressed HBc antigenicity. However, the antigenicity of the HBeAg preparation was pH dependent. At pH 9.6 the HBeAg preparation was non-particulate and expressed HBe antigenicity exclusively; however, at pH 7.2 it was particulate and expressed both HBc and HBe antigenicities. Although this "hybrid" particle most likely does not exist naturally, it is a unique research reagent to investigate the interrelationship between HBcAg and HBeAg. HBcAg was significantly more immunogenic in terms of in vivo antibody production as compared to either the non-particulate or particulate forms of HBeAg. Nevertheless, in most murine strains HBcAg and HBeAg were equivalently immunogenic and crossreactive at the level of T cell activation. The disparity between anti-HBc and anti-HBe antibody production is best explained by the observation that HBcAg can function as a T cell-independent Ag whereas HBeAg is T cell dependent even when present within the same particulate structure as HBcAg. Furthermore, HBcAg was shown to function efficiently as an immunologic carrier moiety for the DNP hapten in athymic as well as euthymic mice in contrast to conventional carrier proteins. These results have implications relevant to the human immune responses to HBcAg and HBeAg during infection, and to vaccine development.

Comparative immunogenicity of hepatitis B virus core and E antigens

The nucleocapsid (hepatitis B core Ag (HBcAg] of the hepatitis B virus is a particulate Ag composed of a single polypeptide (p21). Although a non-particulate form of HBcAg designated hepatitis B e Ag (HBeAg) shares significant amino acid identity, the immune responses to these Ag appear to be regulated independently. This report describes the use of recombinant HBcAg and HBeAg to examine and compare murine T cell and B cell recognition of these related Ag. The HBcAg preparation was stable at pH 7.2 and 9.6 and expressed HBc antigenicity. However, the antigenicity of the HBeAg preparation was pH dependent. At pH 9.6 the HBeAg preparation was non-particulate and expressed HBe antigenicity exclusively; however, at pH 7.2 it was particulate and expressed both HBc and HBe antigenicities. Although this "hybrid" particle most likely does not exist naturally, it is a unique research reagent to investigate the interrelationship between HBcAg and HBeAg. HBcAg was significantly more immunogenic in terms of in vivo antibody production as compared to either the non-particulate or particulate forms of HBeAg. Nevertheless, in most murine strains HBcAg and HBeAg were equivalently immunogenic and crossreactive at the level of T cell activation. The disparity between anti-HBc and anti-HBe antibody production is best explained by the observation that HBcAg can function as a T cell-independent Ag whereas HBeAg is T cell dependent even when present within the same particulate structure as HBcAg. Furthermore, HBcAg was shown to function efficiently as an immunologic carrier moiety for the DNP hapten in athymic as well as euthymic mice in contrast to conventional carrier proteins. These results have implications relevant to the human immune responses to HBcAg and HBeAg during infection, and to vaccine development.

Hepatitis B synthetic immunogen comprised of nucleocapsid T-cell sites and an envelope B-cell epitope

Previous studies located T-cell recognition of the nucleocapsid of the hepatitis B virus (HBcAg) to residues 120-140 in mice bearing the H-2s or H-2b haplotypes. Herein, we demonstrate that B10.S (H-2s) and B10 (H-2b) H-2 congenic strains recognize distinct T-cell sites within the p120-140 (a synthetic peptide corresponding to residues 120-140 of HBcAg) sequence defined by p120-131 and p129-140, respectively. Peptide p120-131 stimulates B10.S HBcAg-primed T cells, and reciprocally p120-131-primed T cells recognize HBcAg. Similarly, the p129-140 sequence is a T-cell recognition site relevant to the native HBcAg in the B10 strain. It is also shown that these 12-residue peptides efficiently prime T-helper cells, which are capable of eliciting antibody production to HBcAg in vivo. These observations prompted us to examine the ability of the HBcAg-specific p120-140 sequence to function as a T-cell carrier moiety as a component of a totally synthetic hepatitis B vaccine. For this purpose a synthetic B-cell epitope from the pre-S(2) region (p133-140) of the viral envelope was chosen because this sequence represents a dominant antibody-binding site of the envelope. Immunization of B10.S and B10 strains with the synthetic composite peptide c120-140-(133-140) elicited anti-peptide antibody production, which was crossreactive with the native viral envelope. Furthermore, c120-140-(133-140) immunization primed p120-131-specific T cells in the B10.S strain and p129-140-specific T cells in the B10 strain, which recognized HBcAg and provided T-helper cell function for anti-envelope antibody production in vivo. These results demonstrate the feasibility of constructing complex synthetic immunogens that represent multiple proteins of a pathogen and are capable of engaging both T and B cells relevant to the native antigens.

Operative management of ipsilateral fractures of the hip and femur

Thirteen patients with ipsilateral hip and femoral shaft fractures are discussed. In nine patients, the femoral shaft fracture was managed by a combination of dynamic compression plating with a medial cancellous bone graft and either multiple cancellous screws or a dynamic hip screw for the proximal fracture (Group I). Four patients had Ender pin fixation (Group II). In Group I, both fractures were united within 16 weeks in all patients, and at least 90% of normal hip and knee motion was regained. Nonunions developed in two of the four Group II patients. Immediate separate fixation of ipsilateral hip and femoral shaft fractures allows definitive management of the proximal fracture and immediate mobilization without external support and provides satisfactory results with a low complication rate.

Comparison of performance of final-year students from three Australian medical schools

Between 1984 and 1986, 888 final-year medical students from The Universities of Sydney, Western Australia and Newcastle took part in trial examinations that comprised multiple-choice questions, modified essay questions and a patient management problem. Differences in student performance among the schools were small. In 1984 and 1985, Newcastle students performed less well than did Sydney students on multiple-choice questions that were prepared by The University of Sydney, but there was no difference between the schools in 1986. Sydney students performed better than did Newcastle students on the multiple-choice question paper that was prepared by The University of New South Wales in 1984, but in the last two years no differences have been detected between the schools in performance on this paper. The performance on modified essay questions in 1984 suggested that Newcastle students were stronger in behavioural sciences and weaker in pathological sciences than were Sydney students. Sydney students performed less well than did Newcastle students in the patient management problem in 1985, particularly in the area of the use of clinical investigations. On the one occasion of testing that involved students from The University of Western Australia (in 1985), these students performed best of the three schools in the patient management problem, and roughly equally with students from Sydney and Newcastle in the multiple-choice question papers. Differences among the schools usually amounted to less than 10% and might have been accounted for by differences in familiarity with test instruments. We conclude that medical students are likely to graduate from The University of Sydney, Western Australia and Newcastle with similar levels of knowledge of internal medicine. Possible differences in problem-solving ability require further study, particularly in the clinical setting.

Antibody production to the nucleocapsid and envelope of the hepatitis B virus primed by a single synthetic T cell site

The nucleocapsid (HBcAg) of the hepatitis B virus (HBV) can induce antibody responses via both a T-cell dependent and a T-cell independent pathway and is highly immunogenic during infection. We have examined the T-cell determinants of the antigen and find that HBcAg-specific helper T cells (TH) can help B cells produce antibody against envelope (HBsAg) antigens as well as HBcAg, even though these antigens are found on separate molecules. We have also been able to prime helper T cells with synthetic T-cell epitopes of HBcAg; helper cells primed with a single synthetic epitope can induce B cells to produce antibody that reacts with multiple HBsAg epitopes. One problem with the development of an HBV vaccine is that some vaccinees and patients do not respond to HBsAg directly; our results indicate that this problem can be circumvented using the response to HBcAg.

Complete amino acid sequence of staphylococcal enterotoxin A

The amino acid sequence of staphylococcal enterotoxin A is presented. Staphylococcal enterotoxin A is a single-chain polypeptide which consists of 233 amino acid residues with a molecular weight of 27,078 and has the amino acid composition Cys2, Asp17, Asn19, Thr16, Ser13, Glu15, Gln12, Pro4, Gly15, Ala7, Val13, Met2, Ile10, Leu23, Tyr18, Phe8, His6, Lys24, Arg7, Trp2, with serine as both amino- and carboxyl-terminal amino acids. Automated sequence analysis of intact enterotoxin A, as well as characterization of the peptides obtained from cyanogen bromide treatment and trypsin and chymotrypsin digestion, led to the elucidation of the complete primary structure of this protein. Less structural homology is observed among staphylococcal enterotoxins A, B (Huang, I-Y., and Bergdoll, M. S. (1970) J. Biol. Chem. 245, 3518-3525), and C1 (Schmidt, J. J., and Spero, L. (1983) J. Biol. Chem. 258, 6300-6306) than that seen between enterotoxins B and C1.

Tibial plateau fractures. A review of operative treatment using AO technique

In a retrospective review of 80 tibial plateau fractures, 28 fractures were treated nonoperatively with a variety of closed methods and 52 were treated with open reduction and internal fixation using AO technique. At an average follow up of 24 months, a satisfactory result was obtained in 87% of the operatively treated patients and in 66% of those treated nonoperatively. It appears that stable, minimally displaced fractures do equally well with closed or open treatment. Patients with depressed, displaced, or unstable fractures did better with operative treatment. When operative treatment is planned the principles and techniques of internal fixation should be carefully followed.

Investigation of synthetic Escherichia coli heat-stable enterotoxin as an immunogen for swine and cattle

In its native form Escherichia coli heat-stable enterotoxin (STa) is nonantigenic; however, neutralizing antibodies are elicited in animals vaccinated with toxin-carrier conjugates. To study the immunogenicity of STa, peptides STa1-18 and STa5-18 were synthesized, characterized, and conjugated to carrier proteins. Pregnant gilts and heifers were hyperimmunized with the respective conjugates. Following parturition neonates were challenged with virulent E. coli (K99+ STa+). Peptides coupled to ovalbumin and emulsified with Freund adjuvant elicited antibodies that neutralized toxin-induced fluid accumulation in suckling mice. Peptides coupled to particulate carriers, with or without muramyl dipeptide adjuvant, failed to induce a measurable response. Peak antibody levels in sera were observed following three doses of conjugate and persisted for several weeks. The serological response in cattle was superior to that observed in swine; however, antibody levels in porcine colostrum were higher than those observed in cattle. Clinical observations of neonates from vaccinated dams indicated that passively obtained antibody provided partial protection from disease, but not as complete as that demonstrable with whole cell bacterins that induce antibody to pili. However, the data suggest the potential for utility of synthetically prepared antigens.

Expression of hepatitis B virus surface and core antigens: influences of pre-S and precore sequences

Amphotropic retroviral expression systems were used to synthesize hepatitis B virus surface antigen (HBsAg) and core antigen. The vectors permitted establishment of cell lines which expressed antigen from either the retroviral long terminal repeat or the mouse metallothionein-I promoter. HBsAgs were synthesized containing no pre-S sequences, pre-S(2) sequences alone, or pre-S(1) plus pre-S(2) sequences. Inclusion of pre-S(2) sequences did not affect the secretion or density of HBsAg particles but did reduce their mass by approximately 30%. Addition of pre-S(1) sequences almost completely abolished secretion of HBsAg and resulted in its localization in an aqueous-nonextractable pre- or early-Golgi cellular compartment. HBsAg was localized to the cytoplasm of the cell. This localization was unaffected by the presence of pre-S sequences in the antigen. Cell lines synthesizing hepatitis B antigens from core DNA fragments, containing or not containing precore sequences, secreted hepatitis B e antigen. However, the absence of precore DNA sequences resulted in additional synthesis of hepatitis core antigen, which was predominantly nuclear in localization.

The major antigen of elastin-associated microfibrils is a 31-kDa glycoprotein

The major antigen derived from elastic fiber microfibrils was identified as a Mr = 31,000 glycoprotein, using immunoblotting and immunohistochemical techniques with antisera raised to "reductive guanidine extracts" of fetal bovine nuchal ligament, and to subfractions of these. A second, elastic fiber-derived, but unidentified, antigen of large molecular size (Mr greater than 200,000) was present in these extracts. Antisera raised to the purified 31-kDa glycoprotein were shown, by immunoelectron microscopy, to localize specifically to the elastin-associated microfibrils. Thus, the macro-molecule was called "microfibril-associated glycoprotein" or MAGP. MAGP is an acidic glycoprotein with a distinctive amino acid composition, being exceptionally rich in glutamic acid, rich in cystine, and low in glycine. MAGP was extractable from tissue homogenates using NaCl, urea, or guanidine hydrochloride solutions, only if a strong reducing agent was present. Thus, disulfide bonding is important for the strong association of MAGP with elastic fibers. Immunoblotting with anti-MAGP antiserum identified two additional reactive species, of Mr = 60,000 and Mr approximately 300,000, in tissue extracts. As only the 31-kDa species was detected in fibroblast culture medium, these additional species were probably aggregates, rather than precursors. MAGP did not react with antilysyl oxidase antiserum on immunoblots or by enzyme-linked immunosorbent assay. MAGP is the first macromolecule to have been established to be a constituent of elastin-associated microfibrils in both developing and mature elastic tissues.

Congenital vertical ocular motor apraxia

The case of a 4 1/2-year-old boy with congenital vertical ocular motor apraxia who was otherwise developmentally and neurologically normal is reported. The presence of perinatal hypoxia in this patient may have been etiologic. While the presence of a supranuclear vertical ocular motor abnormality usually suggests a serious, acquired neurologic or systemic disease it may rarely occur as an isolated congenital finding, as demonstrated in this case.

An evaluation of cefoxitin in the prevention of postoperative infections following orthopedic surgical procedures

An open, nonrandomized study of 25 patients was conducted to evaluate the efficacy of cefoxitin in the prevention of postoperative infection following orthopedic surgical procedures. Cefoxitin was administered in a 2 g dose preoperatively and continued postoperatively at a dose of 2 g every six hours for 72 hours. The mean peak serum level achieved ten minutes after the preoperative dose was 153.7 mcg/ml. The mean bone level in samples taken during the procedure was 10.14 mcg/ml. All patients were monitored postoperatively and at intervals of six weeks, four months and six months for signs of early or late morbidity. No signs of major morbidity were observed in the study group.

Wagner apparatus: a portable traction device for the femur

The Wagner device has proved to be an extremely useful tool for controlling difficult femoral fractures. The fracture and soft tissue injury can be adequately controlled and the patient mobilized by use of the traveling traction principle. This apparatus is easily applied, and the fracture length and alignment can be readily maintained. The device has proven useful in permitting wound care and control. In the complicated polytraumatized patient it facilitates improved pulmonary care and patient hygiene. The advantage the Wagner device affords over conventional traction devices and other external fixation units makes its use a viable orthopaedic alternative.

Cunninghamella bertholletiae wound infection of probable nosocomial origin

After closed reduction and casting of a tibial fracture in a 69-year-old diabetic man, a gangrenous lesion developed under the cast. Cultures of debrided tissue revealed multiple bacteria, including Bacillus sp, plus two fungi, Fusarium sp and a zygomycete identified as Cunninghamella bertholletiae. Large nonseptate hyphae in thrombosed blood vessels suggested that C bertholletiae played a major role in the development of the infection. Recovery of organisms from our patient's wound and from the cast padding suggests that the wound infection was acquired from nonsterile dressings.

Severe intravascular hemolysis after triple valve replacement: cure by replacement of aortic and mitral valves with porcine xenografts

A case report of a patient with a triple cardiac valve replacement complicated by severe postoperative intravascular hemolysis is presented. The patient had neither prosthetic valvular dysfunction nor paravalvular leak and had an excellent hemodynamic response to the operation. Despite intensive medical management, the patient required transfusions of 500 ml of blood every 3 weeks. Replacement of the aortic and mitral prostheses with porcine xenografts alleviated the problem. When a patient requires triple valve replacement, the use of homograft or heterograft valves should be seriously considered as a means of minimizing this potential complication.

Evaluation of ankle fractures: non-operative and operative treatment

A relatively great number of supination abduction fractures did not need surgical treatment because displacement was not present. Significantly better results occurred with operative intervention in supination--eversion and pronation--eversion ankle fractures. Supination--abduction and supination--eversion ankle fractures are best treated by open reduction, anatomical restoration and stabilization of the fractures.

Cardiovascular activity of aromatic guanidine compounds

A series of aromatic guanidines and several 1-phenylbiguanides was prepared and tested for cardiovascular (CV) effects in anesthetized dogs measuring heart rate, blood pressure, carotid artery blood flow, and myocardial force changes. The predominant CV effect at minimally effective dose was vasoconstriction unassociated with cardiac stimulation. The structure-activity relationships of the compounds were discussed comparing their structural similarities to the beta-phenylethylamines. The most potent members of the series were phenylguanidines substituted in the 3 and 4 positions on the aromatic nucleus with hydroxy or chloro groups. Preliminary mechanism studies indicated that the 3,4-dihydroxyphenylguanidines act at least partially by a direct alpha-adrenergic mechanism

Evaluation of arrhythmias in the late hospital phase of acute myocardial infarction compared to coronary care unit ectopy

To evaluate the prevalence and nature of arrhythmias during the entire three-week period in hospital after myocardial infarction, the results of coronary care unit monitoring (initial 3 to 5 days) were compared with continuous 8-hour portable monitoring during the ambulatory phase (second and third weeks) in 83 consecutive survivors. Arrhythmias were detected in 84.3 per cent (70/83) of patients while in the coronary care unit and in 85.5 per cent (71/83) during hospital stay after the coronary care unit. Ventricular ectopic depolarizations were classified as complicated (multifocal, paired, R on T, or five or more a minute) or uncomplicated. Importantly, the high frequency of complicated ventricular extrasystoles and tachycardia persisted during the entire period in hospital (early 34.9% and late 42.5% of all patients). However, only 16.9 per cent (14/83)had these ventricular arrhythmias during both coronary care unit and ward monitoring. Thus, the absence of complicated ventricular ectopic depolarization and ventricular tachycardia in the coronary care unit did not exclude their subsequent occurrence in the majority of the large number of patients with late hospital complicated ventricular ectopy.

Pseudo-malignant lesions in Paget's disease of bone

Two patients with unusual features of Paget's disease are reported. In one patient a circumferential focal and periosteally based mass of Paget's disease presented as a mass lesion superimposed on the sclerotic phase of Paget's disease in the distal femur. Biopsy of the mass showed Paget's disease without neoplasia. The mass has remained unchanged roentgenographically in a 2 year period. In a second patient, a lesion occurred in the mid-portion of the tibia and showed features of the early and radiolucent phase of Paget's disease. In a 4 year period, the lesion has progressed to a more sclerotic phase and to occupy the proximal end of the tibia as well as its mid and lower portions.

The potential of present day lasers as scientific probes for investigating the structure of matter, using an exponenial amplifier

A survey of the techniques required to produce photon energy densities in the range 10(17)-10(25) ergs cm-(3) is given. It is concluded that light amplification using rods cannot achieve these powers and the concept of the exponential amplifier is proposed. It is believed that any laser probe capable of such powers would require the use of neodymium-doped glass. Costs for this ultimate model would be comparable with those for powerful particle accelerators. Initially, the range 10(17)-10(25) ergs cm(-3) could be catered for by conventional flashtube excitation. The upper limits would require excitation by photoemitting diodes, with a 100-A to 200-A band at 8800 A capable of multikilowatt pulsed outputs over 1 cm(2) aperture in a period much less than the 300-700 microsec spontaneous decay time of the laser level. If a suitable sensitizer could be found, then a wider range of photoemitting diodes could be considered.