Accuracy of pedicle screw insertion with and without computer assistance: a randomised controlled clinical study in 100 consecutive patients

We performed a randomised controlled study to assess the accuracy of computer-assisted pedicle screw insertion versus conventional screw placement under clinical conditions. One hundred patients scheduled for posterior thoracolumbar or lumbosacral pedicle screw instrumentation were randomised into two groups, either for conventional pedicle screw placement or computer-assisted screw application using an optoelectronic navigation system. From the computer-assisted group, nine patients were excluded: one because of an inadequate preoperative computed tomography study, seven because of problems with the specific instruments or the computer system, and one because of an intraoperative anesthesiological complication. Thus, there were 50 patients in the conventional group and 41 in the computer-assisted group, and the number of screws inserted was 277 and 219, respectively. There was no statistical difference between the groups concerning age, gender, diagnosis, type of operation performed, mean operating time, blood loss, or number of screws inserted. The time taken for screw insertion was significantly longer in the computer-assisted group. Postoperatively, screw positions were assessed by an independent radiologist using a sophisticated CT imaging protocol. The pedicle perforation rate was 13.4% in the conventional group and 4.6% in the computer-assisted group (P = 0.006). Pedicle perforations of more than 4 mm were found in 1.4% (4/277) of the screw insertions in the conventional group, and none in the computer-assisted group. Complications not related to pedicle screws were two L5 nerve root lesions, one end plate fracture, one major intraoperative bleeding and one postoperative death in the conventional group, and one deep infection in the computer-assisted group. In conclusion, pedicular screws were inserted more accurately with image-guided computer navigation than with conventional methods.

Distribution of interstitial fluid pressure and fluid volumes in hind-limb skin of rats: relation to meridians?

To determine the distribution of interstitial fluid pressure (Pi) and volume (Vi), and to relate the distribution of these parameters to the distribution of potential meridians located by measurement of electrical impedance, we measured Pi, extracellular fluid (Ve) and plasma volumes (Vp) in 14 pre-defined skin areas, 2 x 2 mm, and in concave and convex regions on the hind-limb and groin of rats in control conditions. Pi was measured with sharpened glass capillaries connected to a servo-controlled counter-pressure system, while Ve and Vp were determined as the extravascular distribution spaces of 51Cr-EDTA and 125I-human serum albumin, respectively. Vi was calculated as Ve - Vp, and Vw as the difference between skin wet and dry weight. Grand mean Pi averaged -0.81 mmHg (SD 0.83, n=95). Pi in skin was significantly higher in lateral and medial parts of the medial aspect of hind-limb compared to pressures in the intermediate area (P<0.05). Pressures in the concave groin and the convex knee area were more negative and positive, respectively, than in the flat intermediate central hind-limb area. There was a significantly higher Vi (P<0.05) and Vw (P<0.05) in the lateral side than that in the medial side. Vp was higher medially and laterally than in the intermediate area (P<0.05 for both comparisons), and correlated positively and significantly with Pi (r=0.66, P<0.05). No correlation was found between Pi and electrical impedance. The study suggests that the distribution of Pi, Vi, Vp and Vw is heterogeneous in hind-limb skin at a macroscopic level without obvious relations to potential meridians.

A pilot study on computer-assisted optimal contouring of orthopedic fixation devices

Bending and shaping of longitudinal orthopedic fixation devices like rods and plates is often a difficult and time-consuming process to perform during surgery under sterile conditions. This study presents a novel device for implant contouring and introduces two strategies to obtain parameters necessary for the bending process. The first strategy is based on surgical navigation techniques as established within the framework of computer-assisted orthopedic surgery. Geometrical landmarks, e.g., the location of pedicle screws in a case of posterior spinal fixation, are collected with a three-dimensional pointing device. Subsequently, the final shape of the implant and the associated contouring parameters are calculated. The alternative strategy utilizes a flexible material intended to be used intra-operatively to enable the optimal shape of the implant to be modeled by hand. Contour parameters are calculated from a depth image of this model obtained using an object scanner. Bending of spinal rod systems is used to illustrate both strategies. A newly designed semi-automatic bending machine is proposed to impose the computed deformation on the implant material once parameters are obtained. Integrating the bending device into a system for computer-assisted surgery allows for the interactive control of the contouring process.

A low budget luminometer for sensitive chemiluminescent immunoassays

We have designed a simple luminometer based on a reasonably priced Peltier-cooled charge-coupled device (CCD) camera, housed in a light-tight box, with straightforward lens imaging and a simple platform for a microtitre or other assay format. The quantitative readout of the CCD image is recorded on a PC using customised software. The instrument can be assembled in a standard university workshop for under pound3000, compared with the cheapest commercial instruments retailing at pound10,000 and above. Consistent with the general view on chemiluminescent assays, the sensitivity is 10-100 times greater than that obtained with parallel ELISA's using a chromogenic substrate. A unique feature of the CCD format is that it enables assays to be carried out on arrays of minidots and even nanodots of antigen on the floor of each microtitre well. This permits direct comparison and standardisation of reactivity of a single sample against several antigens and economy in the use of reagents, test sample and technician time; finger-prick samples of blood can be analysed. The instrument should have widespread applicability in developing countries and, indeed, in any laboratories with hard-pressed budgets.

Computer-assisted spine surgery

Computer assistance has been shown to improve significantly the accuracy and safety of pedicle screw insertion under clinical conditions. The technique of image-guided navigation is described in this article, based on the authors' clinical experience of over 4 years. The value of navigation systems for preoperative planning is discussed. Clinical results of the application of this new method in the cervical, thoracic, and lumbosacral spine as well as the iliosacral joints are presented by means of the authors' own studies and reports from the literature. Pros and cons of computer guidance are discussed. The authors predict computer navigation will be used in percutaneous and minimally invasive procedures in the near future.

A new approach to computer-aided spine surgery: fluoroscopy-based surgical navigation

A new computer-based navigation system for spinal surgery has been designed. This was achieved by combining intraoperative fluoroscopy-based imaging using conventional C-arm technology with free-hand surgical navigation principles. Modules were developed to automate digital X-ray image registration. This is in contrast to existing computed tomography- (CT) based spinal navigation systems, which require a vertebra-based registration procedure. Cross-referencing of the image intensifier with the surgical object allows the real-time image-interactive navigation of surgical tools based on one single registered X-ray image, with no further image updates. Furthermore, the system allows the acquisition and real-time use of multiple registered images, which provides an advanced multi-directional control (pseudo 3D) during surgical action. Stereotactic instruments and graphical user interfaces for image-interactive transpedicular screw insertion have been developed. A detailed validation of the system was performed in the laboratory setting and throughout an early clinical trial including eight patients in two spine centers. Based on the resulting data, the new technique promises improved accuracy and safety in open and percutaneous spinal surgery.

Biomechanics of stand-alone cages and cages in combination with posterior fixation: a literature review

Interbody cages in the lumbar spine have met with mixed success in clinical studies. This has led many investigators to supplement cages with posterior instrumentation. The objective of this literature review is to address the mechanics of interbody cage fixation in the lumbar spine with respect to three-dimensional stabilization and the strength of the cage-vertebra interface. The effect of supplementary posterior fixation is reviewed. Only three-dimensional stabilization evaluations in human cadaveric models are included. These studies involve the application of different loads to the spine and the measurement of vertebral motion in flexion-extension, axial rotation, and lateral bending. There are no published studies which detected any differences between different cage designs. However, it does seem that cages inserted from an anterior direction provide better stabilization to the spine than those inserted from a posterior direction. In general, anterior cages stabilize better than posterior cages in axial rotation and lateral bending. Cages from both directions stabilized well in flexion, but not in extension. Supplementary posterior fixation with pedicle or translaminar screws substantially improves the stabilization in all directions. The strength of the cage-vertebra interface from studies using human cadaveric specimens is also reviewed. The axial compressive strength of this interface is highly dependent upon vertebral body bone density. Other factors such as preservation of the subchondral bony end-plate and cage design are clearly less important in the compressive strength. Supplementary posterior instrumentation does not enhance substantially the interface strength in axial compression.

Haemostatic parameters related to lipids and adhesion molecules

Several components of blood, e.g. lipids, coagulation and fibrinolytic factors, are thought to be important risk factors in cardiovascular diseases. The aim of this study was to correlate these risk factors and the soluble adhesion proteins, soluble P-selection (sP-selectin) and soluble vascular cell adhesion molecule (sVCAM-1), in healthy men and women as well as to unravel any effects of smoking. One hundred and forty-two fasting men (median age 36 years) including 39 smokers, and 124 women (median age 34 years) including 35 smokers, were tested between 0800 h and 1000 h. Fibrinogen correlated positively with white blood cells (WBC) (r = 0.25), prothrombin fragment 1.2 (F1.2) (r = 0.21), cholesterol (r = 0.27), beta-thromboglobulin (r = 0.29), Factor VII clotting activity (FVIIc) (r = 0.27) (all P < 0.0001), tissue plasminogen activator antigen (t-PAag) (r = 0.22, P < 0.0005), plasminogen activator inhibitor-1 antigen (PAI-1ag) (r= 0.20) and VCAM-1 (r= 0.19) (both P< 0.002). Cholesterol and triacylglycerol (TG) correlated positively with t-PA antigen (t-PAag) (r = 0.36 and r = 0.38), PAI-1 antigen (PAI-1ag) (r = 0.35 and r = 0.50), P-selectin (r = 0.26 and r = 0.27) (all P < 0.0001) and WBC (r = 0.17, P < 0.007 and r = 0.18, P < 0.004). Cholesterol correlated also with F1.2 (r = 0.29) and TG (r= 0.44) (P< 0.0001). In addition to cholesterol and TG, sP-selectin correlated postively with PAI-1ag (r= 0.39), t-PAag (r= 0.27) and WBC (r = 0.25) (all P < 0.0001). Comparing the various test parameters in men and women, it was found that women had significantly higher levels of F 1.2 and high-density lipoprotein-cholesterol than men, whereas men had higher levels of t-PAag, PAI-lag and P-selectin than women. Smoking was associated with a rise in several of the test parameters. It can be concluded that there are correlations between several risk factors. Of particular interest is the positive correlation between sP-selectin and a number of established risk factors of cardiovascular diseases.

High dose vitamin C counteracts the negative interstitial fluid hydrostatic pressure and early edema generation in thermally injured rats

BACKGROUND AND OBJECTIVE

edema formation after thermal injury is rapid and fulminant within the first hour after injury and increased microvascular permeability has been claimed to be the main responsible mechanism. An acute decrease in interstitial fluid hydrostatic pressure (P(if)) down to -150 mm Hg has recently been reported in dermal burns. This strong negative tissue pressure creates a 'suction' on the fluid in the capillaries. Furthermore, high dose vitamin C (VC) has been shown to reduce postburn edema and fluid requirements following major burn injuries. This led to the present study, aimed at investigating whether VC administered after thermal injury in rats, could attenuate the strongly negative P(if). Edema volume was measured by total tissue water content (TTW) and extravasation of albumin (Ealb).

STUDY DESIGN

a prospective, open experimental study.

MATERIALS AND METHODS

pentobarbital-anesthetized rats received either a full-thickness burn injury covering 10% of total body surface area, or a sham burn. The rats were given VC or equal volumes normal saline (NS) either before the burn, 5 or 30 min after the injury. VC (25 mg/ml in NS, osmolality 272 mOsm/l) was administered as a bolus (66 mg/kg) followed by infusion (33 mg/kg/h). The animals were divided into 7 groups (6 animals in each) according to the timing of VC/NS administration: (1) VC-preburn, (2) VC-5 min postburn, (3) VC-30 min postburn, (4) NS-preburn, (5) NS-5 min postburn, (6) NS-30 min postburn and (7) VC-pre sham burn group. All groups were duplicated for series I and II.

MEASUREMENTS

in series I; P(if) was measured using a sharpened glass micropipette connected to a servo-controlled counter pressure system. Measurements were averaged in the following time periods: preburn, 5-20, 21-40, 41-60 and 61-90 min postburn. In series II; Ealb and TTW were measured in burned and non-burned skin by radio-labelled albumin and wet-dry weights, respectively.

RESULTS

in the sham control group (VC-pre-sham burn), P(if) ranged between -1 and -2 mm Hg and did not change throughout the experimental period. In the NS group (placebo), P(if) fell to -46.8 +/- 10.1 (1 S.D.) mm Hg at 5-20 min after the injury and were -23.1 +/- 13.4 and -11.6 +/- 4.1 mm Hg at 21-40 and 41-60 min postburn. P(if) returned to preburn values at 61-90 min post injury. In the VC groups, there was a marked attenuation of the negative P(if) to average -10.1 +/- 11.8 mm Hg at 5-20 min, -2 +/- 1.7 and -0.6 +/- 1.2 mm Hg at 21-40 and 41-60 min after injury, respectively (all p < 0.01 compared to NS). TTW in burned skin of the NS-5 min groups was 3.12 +/- 0.28, VC5-min group was 2.57+/-0.69 and VC sham was 1.77+/-0.19 ml/g DW, respectively (p < 0.01 compared to sham control for all values). In all the VC-groups TTW values were higher than sham control and lower than in the corresponding NS-groups (p > 0.05 both ways). No statistical significant differences were found between Ealb-values in the VC- and NS-groups.

CONCLUSION

high-dose vitamin C attenuates the development of strongly negative P(if) in burned dermis and reduces the edema as measured by TTW. No significant change in Ealb was found. Vitamin C was thus found to have potential beneficial effects on the acute postburn edema generation.

Work environment and self-rated health as predictors of remaining in work 5 years later among Danish employees 35-59 years of age

In 1990, a random sample of employees (1674 males and 1646 females) in Denmark between 35 and 59 years of age were interviewed about their psychosocial work environment, health, and job satisfaction. In 1995, the cohort was interviewed again regarding present employment status. Predictors from the 1990 interview for remaining in work in 1995 were identified by gender. After controlling for age, very good self-rated health and high development possibilities were found to be independent predictors for remaining in work among males. Among females the predictors were very good self-rated health, high development possibilities, high decision authority, medium level social support and absence of musculoskeletal problems in the knees. In the two extreme 10% risk groups, the "risk" of remaining in work was 58% and 81%, respectively, for males, and 46% and 82% for females.

The 105-kDa protein component of Bacillus cereus non-haemolytic enterotoxin (Nhe) is a metalloprotease with gelatinolytic and collagenolytic activity

A sequence of 91 amino acids residues, probably starting from the N-terminal of the mature protein, was determined for the 105-kDa protein of the non-haemolytic enterotoxin of Bacillus cereus. The last part of this sequence was similar to parts of the N-terminal portions of two collagenases of Clostridium histolyticum and Clostridium perfringens. Zymography, with intact collagen fibril and gelatin as substrates, showed that the 105-kDa protein had collagenolytic and gelatinolytic activity. The 105-kDa protein also showed activity against a typical collagenase substrate, azocoll, and was inhibited by EDTA and 1,10-phenanthroline. We conclude that the 105-kDa protein is a collagenase.

The sequence of the non-haemolytic enterotoxin operon from Bacillus cereus

The non-haemolytic enterotoxin from Bacillus cereus has been sequenced. It is composed of three components, non-haemolytic enterotoxin A, B and C of 41.0, 39.8 and 36.5 kDa, respectively. Transcription of the operon seems to be positively regulated by plcR, a gene that also regulates phospholipase C expression. There is substantial similarity between the three proteins of non-haemolytic enterotoxin and between the non-haemolytic enterotoxin and haemolytic enterotoxin proteins.

Cutting edge: homologous recombination of the MHC class I K region defines new MHC-linked diabetogenic susceptibility gene(s) in nonobese diabetic mice

To localize the MHC-linked diabetogenic genes in the nonobese diabetic (NOD) mouse, a recombinational hotspot from the B10.A(R209) mouse was introduced to the region between the MHC class I K and class II A of the NOD mouse with the recombinational site centromeric to the Lmp2/Tap1 complex by breeding the two strains. Replacement of the NOD region centromeric to the recombinational site with the same region in R209 mice prevented the development of diabetes (from 71 to 3%) and insulitis (from 61 to 15%) in the N7 intra-MHC recombinant NOD mice. Similarly, the replacement of the NOD class II A, E and class I D region with the same region in R209 mice prevented the diseases (diabetes, from 71 to 0%; insulitis, from 61 to 3%). In addition to the MHC class II genes, there are at least two MHC-linked diabetogenic genes in the region centromeric to Lmp2.

DNA vaccination favours memory rather than effector B cell responses

Following priming and boosting of mice with a DNA vector pEE6DeltaS-hCGss expressing sequences encoding a transmembrane version of the beta-chain of human chorionic gonadotropin (hCGbeta), we failed to detect appreciable levels of specific antibody. However, subsequent challenge with hCG protein in Ribi adjuvant elicited a strong and rapid secondary immune response. This response was of comparable magnitude to that produced following priming, boosting and challenge with protein in adjuvant. Thus, DNA vaccination with this vector is as efficient in generating B cell memory as is conventional immunization, but the memory generation occurs in the absence of an overt effector response. Despite an overall similar level of specific antibody, the DNA-vaccinated mice produced hCG-specific antibodies biased towards IgG2a and IgG2b isotypes, whereas the protein-vaccinated mice produced higher levels of IgG1 antibodies. Both Th1 and Th2 cytokines (interferon-gamma (IFN-gamma) and IL-4) were lower in the spleens of the DNA-immunized animals compared with the protein-Ribi-immunized animals, possibly suggesting a different level of helper T cell response to the two different modes of immunization.

Dual specificity antibodies using a double-stranded oligonucleotide bridge

The covalent conjugation of oligonucleotides to antibody Fab' fragments was optimized by using oligonucleotides modified with a hexaethylene linker arm bearing three amino groups. One oligonucleotide was coupled to antibody of one specificity and a complementary oligonucleotide to antibody of a second specificity. The antibodies were then allowed to hybridize by base pairing of the complementary nucleotide sequences and the generation of bispecific antibody was analyzed on SDS-PAGE and confirmed using BIAcore analysis. The strategy of complementary oligonucleotide-linked bispecific molecules is not limited to antibodies but is applicable to linking any two molecules of different characteristics.

The external spinal fixator does not reduce anterior column motion under axial compressive loads. A mechanical in vitro study

We performed an in vitro study to investigate the effect of external spinal fixation on anterior column motion under physiological axial compression loading. The AO external spinal fixator (ESF) was applied to 5 human cadaveric lumbar spine specimens (L3-S1) at levels L4 to S1. All specimens were tested in 4 configurations: i) intact, ii) ESF in a neutral position, iii) ESF in distraction (12 mm), and iv) ESF in compression (8-12 mm). Cyclic sinusoidal axial compressive loads from 60 to 600 N were applied for 10 cycles in each test condition. The axial displacement of the load application point was recorded as an indicator of anterior column axial translation. The axial motion with the fixator in distraction was significantly greater than all other conditions, including intact. Compression of the fixator resulted in the least axial displacement. External fixation in the neutral position did not significantly affect the overall axial translation, when compared to the intact state. In conclusion, the external spinal fixator did not significantly reduce anterior column axial translation and, in distraction, this motion exceeded that of the intact specimen. Since pain relief is frequently observed during distraction of the painful segment/s with the external fixator, the mechanical basis of the pain relief is not well understood.

[Frostbite injuries]

Frostbite injuries occur mainly in toes, fingers, ears, nose and cheek. Typically an initial vasoconstriction in the skin will protect from drop in core temperature. Ice crystal development occurs when tissue temperature drops to -2 degrees C, leading to increased osmolality of the extracellular fluid and intracellular dehydration. An additional insult occurs with thawing due to reperfusion of the tissue and thereby release of inflammatory mediators. Symptoms of frostbite injury are: White-cyanotic discoloration, pain and numbness followed by hypoaesthesia. General hypothermia should be prevented and treated before managing the local frostbite injuries. Direct contact with warm skin without rubbing should be used in superficial injuries. More severe and deeper injuries should not be thawed until definite treatment could be given in a hospital. Re-freezing and mechanical influence on the injured parts must be avoided. Thawing should preferably be done in stirred water of 40-42 degrees C with mild soap. Antibiotics may be indicated when the skin barrier is broken. Surgical debridement should be postponed until a clear demarcation occurs.

The effect of melatonin on cellular activation processes in human blood

The pineal hormone melatonin, due to its lipophilic nature, has access to every cell and every part of a cell in the body, suggesting that it could exert effects on blood immune cells. The regulation of the activation of monocytes may be important in a number of diseases, especially pathophysiological conditions associated with inflammatory reactions. Considering this, a study on the effect of melatonin on monocytes in whole blood was carried out. Melatonin added at a final concentration of 5 ng/mL to whole blood in vitro reduced lipopolysaccharide (LPS)-induced tissue factor (TF) activity in monocytes by 55% in blood from a group of subjects with melatonin-sensitive cells. At even lower concentrations of melatonin (20-50 pg/mL) and in the physiological range, a trend of suppressed LPS-induced TF activity by approximately 20% was seen. A further indication of a downregulation of LPS-stimulated monocytes by melatonin was shown by its reduction of LPS-induced tumor necrosis factor (TNF). Twenty to one hundred pg/mL melatonin caused a significant reduction of LPS-induced TNF production by approximately 25-30%. In contrast, melatonin at a final concentration of 10 pg/mL, added to whole blood incubated with LPS and also the phorbol ester, PMA, caused a significant rise of 25%; whereas 100 pg/mL enhanced LPS + PMA-induced TNF by approximately 80% as compared to LPS + PMA alone. These effects were not detectable during the winter darkness of Tromsø (70 degrees N), probably due to the high content of melatonin in the blood even at daytime. These results show that melatonin may have a beneficial effect by suppressing the expression of TF activity in LPS-stimulated monocytes. Furthermore, the results indicate that LPS-induced TF in monocytes of whole blood is independent of protein kinase C (PKC) activation. Melatonin is probably amplifying cellular activation reactions that are PKC-dependent. This may be physiologically important in upregulation of the immune system.

Bayesian predictive identification and cumulative classification of bacteria

In this paper we give a mathematically precise formulation of an old idea in bacterial taxonomy, namely cumulative classification, where the taxonomy is continuously updated and possibly augmented as new strains are identified. Our formulation is based on Bayesian predictive probability distributions. The criterion for founding a new taxon is given a firm theoretical foundation based on prediction and it is given a clear-cut interpretation. We formulate an algorithm for cumulative classification and apply it to a large database of bacteria belonging to the family Enterobacteriaceae. The resulting taxonomy makes microbiological sense.

Epinephrine promotes IL-8 production in human leukocytes via an effect on platelets

Interleukin-8 (IL-8) is generally accepted to be an important mediator of a number of acute and chronic inflammatory diseases and is produced by monocytes upon stimulation by lipopolysaccharide (LPS). Epinephrine has been reported by several groups to suppress activation of monocytes in response to LPS, and the aim of the present study was to examine the effect of epinephrine on LPS induced IL-8 production using whole blood as a model system. Epinephrine increased LPS induced IL-8 production in a dose-dependent manner in the whole concentration range (0.001-100 microM) and 1 microM epinephrine increased IL-8 levels with 125%. Epinephrine per se had no effect on IL-8 levels. The potentiating effect of epinephrine was mediated by blood platelets, since IL-8 levels in samples containing platelets and stimulated with LPS and epinephrine (1-100 microM) were significantly higher (p<0.05) than in control samples containing no platelets. This effect of platelets seemed to be due to platelet release products, since addition of 25 microL platelet lysate supernatant to whole blood increased LPS induced IL-8 production with 100% and a similar effect was observed in freshly isolated mononuclear cells resuspended in plasma. Upon addition of 50 microg/ml of the carboxyterminal peptide of platelet factor 4 (PF4(58-70)) to whole blood, LPS stimulated IL-8 levels were increased with 115%, whereas in mononuclear cells, 20 microg/ml PF4(58-70) enhanced IL-8 production with 40%. We demonstrate for the first time that epinephrine promotes LPS induced production of IL-8 in whole blood via an effect on blood platelets. This potentiating effect of platelets is shown to be due to platelet granule contents, and platelet factor 4 (PF4) is suggested to be one of several platelet granule proteins promoting LPS induced IL-8 production in whole blood.

Attributional style and its relation to other personality dispositions

BACKGROUND

People vary greatly with respect to the way they explain negative events (personal failures), and this variation in attributional style seems to be related to various personality traits and also academic performance. For example, the theory of learned helplessness regards a pessimistic attributional style as an important determinant in the development of depression.

AIM

The primary purpose of the present study was to compare attributions for positive and negative events with respect to correlations with seven personality dispositions. The comparisons concern the three attributional dimensions internality, stability and globality, as well as their combination. The hypothesis was that attributions for positive events are differently correlated with the seven personality dispositions than are attributions for negative events.

SAMPLE

166 advanced teacher students (132 females and 34 males).

METHOD

On the basis of an inventory the students were given scores on the attributional variables (related to imagined positive and negative academic events), global and academic self-esteem, motive to seek success, motive to avoid failure, self-efficacy, defensiveness, and depression.

RESULTS

The hypothesis was confirmed. Attributions for positive events correlated differently with the seven personality dispositions than attributions for negative events. Also, factor analysis of the attributional dimensions indicated that attributions for positive events measured quite different components than attributions for positive events.

CONCLUSION

The general conclusion is that both event kinds should be considered when using attributional style for predicting or explaining personality and behavioural variables.

The effect of low-profile serine substitutions in the V3 loop of HIV-1 gp120 IIIB/LAI on the immunogenicity of the envelope protein

Many microbial antigens contain powerful hypervariable epitopes that fail to induce broadly protective immunity because they dominate the immune response at the expense of more conserved but weaker epitopes. If the undesired B cell epitopes are eliminated, the immune system could be focused on the conserved epitopes and produce a stronger antibody response to conserved parts of the protein and thus become a more efficacious immunogen for a vaccine. We examined this possibility using the human immunodeficiency virus envelope glycoprotein (gp)120 IIIB/LAI and selectively replaced the amino acids from the V3 region and analyzed the overall immunogenicity of the mutant proteins after nucleic acid immunization in mice. The most variable residues of the human immunodeficiency virus type 1 gp120 V3 loop sequence were replaced with serine, which has a small uncharged hydrophilic side chain and therefore is likely to be less immunogenic than amino acids found in wildtype V3 sequences. The serine substitutions did not affect the ability of soluble CD4 to bind the mutant molecules compared with wildtype gp120 and monoclonal antibodies against both linear and discontinuous epitopes located in the V1/V2, C1, and C4 regions of the molecule. These data suggest that the V3 loop substitutions did not grossly affect the overall conformation of the envelope molecule. Immunization of CBA x BALB/c F1 mice with DNA expression plasmids for the wild-type gp120 sequence induced a predominantly IgGI antibody response with end point titers of 10(4)-5 x 10(4). The antibodies reacted only with conformationally intact gp120. Serine replacements targeted to both sides of the V3 loop had a major impact on gp120 immunogenicity, with a markedly reduced response in the majority of animals tested. Analysis of the epitope specificity of the responses suggests that N-terminal amino acids in the V3 loop contribute to the major immunodominant epitope and provides no evidence that their removal enhances immunogenicity of the conserved regions.

Sampling of interstitial fluid and measurement of colloid osmotic pressure (COPi) in pigs: evaluation of the wick method

The wick method for sampling of interstitial fluid from subcutis was applied in fluid balance studies in young pigs. Colloid osmotic pressure was measured in serum (COPs) and interstitial fluid (COPi) using a membrane colloid osmometer. Our aims were to determine the 'true' COPi, and to find the optimal duration of wick implantation. In series I (n = 6) a 'crossover' experiment was performed using wicks soaked in different priming solutions (non-diluted and diluted serum protein solutions or isotonic salt solution). Circulatory arrest was induced just before wick insertion in order to eliminate the vascular part of the acute inflammation. In series II (n = 6) wicks were removed in sequence after 60, 90, 120 and 180 min sampling time in anaesthetized pigs in vivo. COPs, COPi and haematocrit (HCT) together with haemoglobin (Hgb), serum albumin and total protein concentrations were determined in the same animals. In series I average COPs and COPi were 13.7 (1.4) and 7.2 (1.4) mmHg respectively (SD). In series II the optimal wick implantation times were estimated to be 60-90 min for wicks soaked in diluted protein solution, and 90-120 min for dry and saline-soaked wicks. COPs averaged 13.0 (0.7) mmHg, HCT 30.0 (1.6)%, Hgb 8.3 (0.9) g/dl, s-albumin 22.7 (0.6) g/l and s-protein 47.3 (2.3) g/l. Compared to commonly reported reference values, we found surprisingly low values for most of the measured variables. This may be related to the fact that we used immature pigs. An analysis of the validity of the wick method based on our own results and published reports is presented. We conclude that sampling of interstitial fluid with subcutaneous wicks is easy to perform in young pigs. However, the COP-values measured in wick fluid have to be carefully evaluated especially when sampling is performed in vivo.