T cell circuits that sense antigen density with an ultrasensitive threshold

Overexpressed tumor-associated antigens [for example, epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor 2 (HER2)] are attractive targets for therapeutic T cells, but toxic "off-tumor" cross-reaction with normal tissues that express low levels of target antigen can occur with chimeric antigen receptor (CAR)-T cells. Inspired by natural ultrasensitive response circuits, we engineered a two-step positive-feedback circuit that allows human cytotoxic T cells to discriminate targets on the basis of a sigmoidal antigen-density threshold. In this circuit, a low-affinity synthetic Notch receptor for HER2 controls the expression of a high-affinity CAR for HER2. Increasing HER2 density thus has cooperative effects on T cells-it increases both CAR expression and activation-leading to a sigmoidal response. T cells with this circuit show sharp discrimination between target cells expressing normal amounts of HER2 and cancer cells expressing 100 times as much HER2, both in vitro and in vivo.

Asymptomatic De Novo Inflammatory Bowel Disease Late After Liver Transplantation for Primary Sclerosing Cholangitis: A Case Report

Guidelines recommend colonoscopy screening for possible asymptomatic inflammatory bowel disease (IBD) in all patients diagnosed with primary sclerosing cholangitis (PSC). PSC-IBD warrants regular dysplasia-surveillance colonoscopy. However, no consensus exists regarding follow-up colonoscopy in PSC patients without IBD who remain asymptomatic. We describe a 43-year-old female who had undergone liver transplantation (LT) due to advanced PSC. Previous colonoscopies had been normal. The post-transplantation course was uneventful, with no rejections and signs of PSC recurrence. Immunosuppression was by tacrolimus monotherapy. She was asymptomatic with normal inflammation markers. A protocol colonoscopy, performed as general dysplasia surveillance 8 years post-transplantation, revealed mucopurulent-covered small superficial ulcerations and erythema diffusely distributed from the cecal to sigmoid colon with intervening normal mucosa and rectal sparing. Histologic examination showed patchy chronic colitis with crypt architectural distortion and mild-moderate inflammation activity. Infection samples were negative. Findings complied with de novo IBD, type unclassified. In conclusion, the link between PSC and clinically silent IBD may manifest after the PSC diagnosis and even several years after LT. Given the increased colorectal cancer risk associated with PSC, IBD, and LT, repeat colonoscopy might be warranted in PSC patients without IBD at initial assessment, and also after LT.

Contributions of climate, leaf area index and leaf physiology to variation in gross primary production of six coniferous forests across Europe: a model-based analysis

Gross primary production (GPP) is the primary source of all carbon fluxes in the ecosystem. Understanding variation in this flux is vital to understanding variation in the carbon sink of forest ecosystems, and this would serve as input to forest production models. Using GPP derived from eddy-covariance (EC) measurements, it is now possible to determine the most important factor to scale GPP across sites. We use long-term EC measurements for six coniferous forest stands in Europe, for a total of 25 site-years, located on a gradient between southern France and northern Finland. Eddy-derived GPP varied threefold across the six sites, peak ecosystem leaf area index (LAI) (all-sided) varied from 4 to 22 m(2) m(-2) and mean annual temperature varied from -1 to 13 degrees C. A process-based model operating at a half-hourly time-step was parameterized with available information for each site, and explained 71-96% in variation between daily totals of GPP within site-years and 62% of annual total GPP across site-years. Using the parameterized model, we performed two simulation experiments: weather datasets were interchanged between sites, so that the model was used to predict GPP at some site using data from either a different year or a different site. The resulting bias in GPP prediction was related to several aggregated weather variables and was found to be closely related to the change in the effective temperature sum or mean annual temperature. High R(2)s resulted even when using weather datasets from unrelated sites, providing a cautionary note on the interpretation of R(2) in model comparisons. A second experiment interchanged stand-structure information between sites, and the resulting bias was strongly related to the difference in LAI, or the difference in integrated absorbed light. Across the six sites, variation in mean annual temperature had more effect on simulated GPP than the variation in LAI, but both were important determinants of GPP. A sensitivity analysis of leaf physiology parameters showed that the quantum yield was the most influential parameter on annual GPP, followed by a parameter controlling the seasonality of photosynthesis and photosynthetic capacity. Overall, the results are promising for the development of a parsimonious model of GPP.

Predicting the decline in daily maximum transpiration rate of two pine stands during drought based on constant minimum leaf water potential and plant hydraulic conductance

The effect of drought on forest water use is often estimated with models, but comprehensive models require many parameters, and simple models may not be sufficiently flexible. Many tree species, Pinus species in particular, have been shown to maintain a constant minimum leaf water potential above the critical threshold for xylem embolism during drought. In such cases, prediction of the relative decline in daily maximum transpiration rate with decreasing soil water content is relatively straightforward. We constructed a soil-plant water flow model assuming constant plant conductance and daily minimum leaf water potential, but variable conductance from soil to root. We tested this model against independent data from two sites: automatic shoot chamber data and sap flow measurements from a boreal Scots pine (Pinus sylvestris L.) stand; and sap flow measurements from a maritime pine (Pinus pinaster Ait.) stand. To focus on soil limitations to water uptake, we expressed daily maximum transpiration rate relative to the rate that would be obtained in wet soil with similar environmental variables. The comparison was successful, although the maritime pine stand showed carry-over effects of the drought that we could not explain. For the boreal Scots pine stand, daily maximum transpiration was best predicted by water content of soil deeper than 5 cm. A sensitivity analysis revealed that model predictions were relatively insensitive to the minimum leaf water potential, which can be accounted for by the importance of soil resistance of drying soil. We conclude that a model with constant plant conductance and minimum leaf water potential can accurately predict the decline in daily maximum transpiration rate during drought for these two pine stands, and that including further detail about plant compartments would add little predictive power, except in predicting recovery from severe drought.

Summary models for light interception and light-use efficiency of non-homogeneous canopies

The application of detailed models of canopy photosynthesis rely on the estimation of attenuation of light in the canopy. This attenuation is readily estimated with the Lambert-Beer law when the canopy is homogeneous. In reality, forest canopies are far from homogeneous, and this has led to the use of detailed light extinction models that account for grouping of foliage between and within trees. Because such models require detailed parameterization and fine resolution inputs, they are impractical in larger-scale applications. Thus, there is interest in simplified models that can be readily parameterized. We developed two equations that can be used to estimate mean annual light interception by single unshaded trees and by stands of Poisson distributed trees. Interception by single trees is a function of crown surface area, the ratio of leaf area to crown surface area, the extinction coefficient in a homogeneous canopy--which can be determined separately--and one empirical parameter that depends on the mean solar angle. The summary model was tested against a detailed model of interception, and showed good agreement, although with slight bias. The results showed that crown surface area is a good summary variable for crown size and shape, because errors are independent of crown shape (ellipsoids, cones and height:width ratios). We also tested whether canopy photosynthesis is proportional to light interception across canopies differing in structure and leaf area index, and found that light-use efficiency is influenced by canopy structure. The model is useful in larger-scale applications because it can be parameterized with available data without the need for additional empirical parameters. It can also be used to study the effect of stand structure on mean annual light interception and productivity.

The ratio of NPP to GPP: evidence of change over the course of stand development

Using Scots pine (Pinus sylvestris L.) in Fenno-Scandia as a case study, we investigate whether net primary production (NPP) and maintenance respiration are constant fractions of gross primary production (GPP) as even-aged mono-specific stands progress from initiation to old age. A model of the ratio of NPP to GPP is developed based on (1) the classical model of respiration, which divides total respiration into construction and maintenance components, and (2) a process-based model, which derives respiration from processes including construction, nitrate uptake and reduction, ion uptake, phloem loading and maintenance. Published estimates of specific respiration and production rates, and some recent measurements of components of dry matter in stands of different ages, are used to quantify the two approaches over the course of stand development in an average environment. Both approaches give similar results, showing a decrease in the NPP/GPP ratio with increasing tree height. In addition, we show that stand-growth models fitted under three different sets of assumptions-(i) annual specific rates of maintenance respiration of sapwood (mW) and photosynthesis (sC) are constant; (ii) m(W) is constant, but sC decreases with increasing tree height; and (iii) total maintenance respiration is a constant fraction of GPP and s(C) decreases with increasing tree height-can lead to nearly identical model projections that agree with empirical observations of NPP and stand-growth variables. Remeasurements of GPP and respiration over time in chronosequences of stands may be needed to discern which set of assumptions is correct. Total (construction + maintenance) sapwood respiration per unit mass of sapwood (kg C (kg C year)-1) decreased with increasing stand age, sapwood stock, and average tree height under all three assumptions. However, total sapwood respiration (kg C (ha year)-1) increased over the course of stand development under (i) and (ii), contributing to a downward trend in the time course of the NPP/GPP ratio after closure. A moderate decrease in mW with increasing tree height or sapwood cross-sectional area had little effect on the downward trend. On the basis of this evidence, we argue that a significant decline in the NPP/GPP ratio with tree size or age seems highly probable, although the decline may appear insignificant over some segments of stand development. We also argue that, because stand-growth models can give correct answers for the wrong reasons, statistical calibration of such models should be avoided whenever possible; instead, values of physiological parameters should come from measurements of the physiological processes themselves.

The fixation properties of carbon fiber-reinforced liquid crystalline polymer implant in bone: an experimental study in rabbits

A novel composite material with ultra-high strength and a low elastic modulus called carbon fiber-reinforced liquid crystalline polymer (LCP/CF) has been developed. We studied the fixation properties of an intramedullary LCP/CF rod in rabbit bone. The medullary canals of both femora were reamed with a drill 3.2 mm in diameter starting from the trochanteric fossa in eleven New Zealand White rabbits weighing on average 4.8 kg. A smooth LCP/CF rod 3.2 mm in diameter and 50 mm in length was introduced into the medullary canal of both femora. The follow-up intervals were 0, 6, 12, and 52 weeks. The upper part of the harvested femora was cut into two pieces, each 25 mm in length. A mechanical push-out test was performed within 48 h to determine bone-implant interface attachment strength in the proximal (cancellous) and distal (cortical) locations. The mean push-out strength values at 0, 6, 12, and 52 weeks were 61, 250, 382, and 612 KPa in the cancellous location and 0, 32, 41, and 68 KPa in the cortical location, respectively. The strength of the bone/implant interface appeared to be quite low, similar to other uncoated or nonporous implants, but it was found to increase with time.

Fine root biomass of Scots pine stands differing in age and soil fertility in southern Finland

The biomass of small and large fine roots (</= 2 mm and 2-5 mm in diameter, respectively) in mineral soils of southern Finland was compared with estimated foliage biomass in the same stands. Study material was collected from stands differing in site fertility and age. The humus layer was deeper at the more fertile sites than at the less fertile sites. Fine root density was greater in humus than in mineral soil, and the fine root density in mineral and humus layers was greater at the less fertile sites than at the more fertile sites. Although the amount of fine root biomass was not correlated with any commonly recorded stand characteristic, small fine root biomass was proportional to foliage biomass for both site types. The coefficient of proportionality was larger for the less fertile sites than for the more fertile sites, supporting the theory of functional balance. A similar relationship could not be established for the large fine roots. A trend of increasing fine root:needle mass ratio with stand age was observed for stands on the less fertile sites.

Fixation of distal femoral osteotomy with an intramedullary rod: early failure of carbon fibre composite implant in rabbits

A novel composite material with an ultra-high strength and a low elastic modulus, comprising a carbon fibre reinforced liquid crystalline polymer (LCP/CF) has been developed. An experimental osteotomy of the distal femur in nineteen rabbits weighing on average 4.8 (3.7-6.3) kg was fixed with an intramedullary LCP/CF rod of 3.2 mm in diameter and 50 mm in length. The initial mechanical properties of the rods had a mean shear strength of 180 MPa, a flexural strength of 450 MPa, and a flexural modulus of 40 GPa. The rods were implanted for periods of 3, 6, 12, 24, and 52 weeks. The healing of the osteotomy was analyzed by radiographic, histological, microradiographic, and oxytetracycline fluorescence studies. The strength retention of the LCP/CF rods was measured by mechanical testing. Solid union of the osteotomy was seen within 6 weeks. The implants retained their original strength properties up to 52 weeks. In three rabbits, a non-union with granulation tissue and carbon fibre particles was noticed at the osteotomy site, where disruption of the implant surface was seen at the level of the osteotomy. Further studies with a special interest in the fabrication process of the LCP/CF-implants are needed.

Fixation of femoral shaft osteotomy with an intramedullary composite rod: an experimental study on dogs with a two-year follow-up

A novel composite material with an ultra-high strength and a low elastic modulus called carbon fibre-reinforced liquid crystalline polymer (LCP/CF) has been developed. An experimental diaphyseal osteotomy of the proximal femur in fourteen Beagle dogs was fixed with an intramedullary LCP/CF rod of 4.5 mm in diameter and 80 mm in length. The radiological follow-up intervals were 1, 3, 6, 12, 24, 52, and 104 weeks. Five dogs were killed at 1 year and three dogs at 2 years for histological studies; six dogs were retained for longer follow-up. Radiographs showed an uncomplicated healing of the diaphyseal osteotomy with an external callus formation in all dogs in 12 weeks. Histological analysis revealed a benign host tissue response with few inflammatory cells. Both bone and fibrous tissue were seen at the LCP/CF-host tissue interface. The cross-sectional cortical area of the operated femur was slightly greater than that of the control femur in the 2-year follow-up. LCP/CF showed promising properties for high-load applications.

Phospholipase A2 activity in body fluids and pancreatic tissue in patients with acute necrotising pancreatitis

OBJECTIVE

To measure pancreatic and non-pancreatic phospholipase A2 activity in human acute necrotising pancreatitis.

DESIGN

Prospective study.

SETTING

University hospital, Finland.

SUBJECTS

20 patients with acute necrotising pancreatitis.

INTERVENTIONS

Serum and urine samples were taken daily for a week and fluid from peritoneal lavage for six days after admission. Samples from the pleural cavity were taken from patients in whom pleural drainage was considered necessary. Pancreatic tissue was recovered from the patients who were operated on for acute pancreatitis or for pancreatic tumour.

MAIN OUTCOME MEASURES

Serum phospholipase A2, amylase, and lipase activities.

RESULTS

Serum phospholipase A2 activity increased up to eightfold, 25.0 (5.4) IU/L (n = 20, range 9.0-77 IU/L) (reference value <3 IU/L) and remained high during the first week, whereas serum amylase and lipase returned to the reference range during the first four days. The maximal phospholipase A2 activity in urine was 4.5 IU/L, in the fluid from peritoneal lavage 16.9 IU/L, and in the fluid from the pleural cavity 37.0 IU/L. Phospholipase A2 activity in necrotic pancreatic tissue ranged from 0.25 to 5.70 IU/g and in normal pancreatic tissue from 9.85 to 15.0 IU/g. Preincubation at 60 degrees C showed non-pancreatic phospholipase A2 activity predominated in serum, whereas part of the enzyme activity in the fluids from pleural cavity and peritoneal lavage proved to be of pancreatic derivation.

CONCLUSIONS

The results suggest a role for both pancreatic and non-pancreatic phospholipase A2 in acute pancreatitis. Preincubation at 60 degrees C proved useful in the differentiation between pancreatic and non-pancreatic phospholipase A2 activity.

The effect of an intramedullary carbon-fiber-reinforced liquid crystalline polymer implant on bone: an experimental study on rabbits

A novel composite material with an ultra-high strength and a low elastic modulus called carbon-fiber-reinforced liquid crystalline polymer (LCP/CF) has been developed. We studied the effects of an intramedullary LCP/CF rod on bone in rabbits. A LCP/CF rod of 3.2 mm in diameter and 50 mm in length was introduced into the intramedullary canal of the right femur in ten rabbits weighing an average of 3.6 (3.1-4.2) kg. The follow-up intervals were 3 and 52 weeks. No signs of deformity or osteopenia were seen in the operated femurs in the radiographic, histological, and histomorphometric studies. Histologically, the implant was enclosed by cancellous bone in the metaphyseal area and by a thin cancellous bone cuff in medullary cavity. Bone was able to grow in direct contact with the LCP/CF rod. No signs of degradation of the implants or of adverse tissue reaction were seen. The intramedullary LCP/CF rod had no harmful effects on bone in rabbits. The biocompatibility of the LCP/CF appeared to be good. This novel composite material demonstrates properties that may be useful in orthopedic applications.

Duodenal secretion of phospholipase A2, amylase, and bicarbonate in chronic pancreatitis

Phospholipase A2 has been suggested to be involved in the pathogenesis and pathophysiology of acute pancreatitis. We determined phospholipase A2 and amylase activities in duodenal juice collected during a secretin test from 30 consecutive patients who were suspected to have chronic pancreatitis or biliary disease. The patients underwent endoscopic retrograde cholangiopancreatography (ERCP) the following day. In the 8 patients with ERCP findings of advanced chronic pancreatitis, the mean outputs of phospholipase A2, amylase, and bicarbonate were reduced by 74%, 72%, and 60% compared to the respective values in the 13 (control) patients without a diagnosis of any pancreatic disorder or jaundice. In the 3 patients with recurrent pancreatitis but normal ERCP findings and in the 6 patients with jaundice the output values were not significantly reduced compared to those in the patients without any pancreatic disorder or jaundice. The outputs of amylase and phospholipase A2 were not significantly interrelated, whereas the outputs of phospholipase A2 and bicarbonate correlated well. Receiver characteristic (ROC) curves confirmed the high specificity and sensitivity of phospholipase A2 or bicarbonate output in patients with ERCP findings of advanced chronic pancreatitis compared to those with no changes in pancreatic ducts, with similar probability values of 0.880 +/- 0.111 (SEM), compared to the respective lower value of amylase, 0.676 +/- 0.118. Phospholipase A2 and bicarbonate output proved of equal value as markers of chronic pancreatitis and were superior to amylase output in the secretin test.

Serum phospholipase A2, amylase, lipase, and urinary amylase activities in relation to the severity of acute pancreatitis

OBJECTIVE

To compare serum phospholipase A2 activity with measurements of conventional enzymes as an indicator of the severity of acute pancreatitis.

DESIGN

Prospective study.

SETTING

University hospital, Finland.

SUBJECTS

80 Consecutive patients with acute pancreatitis.

INTERVENTIONS

Serum and urine samples were taken daily for a week after admission.

MAIN OUTCOME MEASURES

Serum phospholipase A2, amylase, lipase, and urinary amylase activities.

RESULTS

On admission, the serum amylase and lipase activities increased in parallel in all patients. However, the mean serum phospholipase A2 activity was three times higher in the patients with acute fulminant pancreatitis than in those with milder disease. The phospholipase A2 activity remained high during the course of the severe disease, whereas the other enzyme activities decreased appreciably during the first week. In contrast to the other enzyme activities that of serum phospholipase A2 correlated well with the severity of the acute pancreatitis. Heating at 60 degrees C for 45 minutes to inactivate the non-pancreatic thermolabile phospholipase A2 reduced the total serum phospholipase A2 activity more than the enzyme activity in the homogenates of pancreatic tissue, which suggests that extrapancreatic phospholipase A2 is present in serum. The receiver operating characteristic (ROC) curves confirmed the high sensitivity and specificity of serum phospholipase A2 activity with a mean (SEM) area under the curve up to 0.870 (0.062) compared with the other enzyme activities of which the highest area under the curve was 0.52 (0.089).

CONCLUSIONS

In contrast to amylase and lipase activities, measurement of serum phospholipase A2 activity is important in the assessment of the severity of acute pancreatitis so that optimal treatment may be given.

Inhibition of serum phospholipase-A2 in acute pancreatitis by pharmacological agents in vitro

Phospholipase-A2 has been suggested as having a role in the pathophysiology of acute pancreatitis. The inhibition of phospholipase-A2 was studied in vitro using 17 pharmacological agents in the search for a specific therapy for acute pancreatitis. The inhibitory effect was tested using an isotopic assay system with 2-palmitoyl-(1-14C)-labelled dipalmitoyl phosphatidylcholine as a substrate and 10 microliters of serum from patients with acute necrotizing pancreatitis as an enzyme source. Among all agents tested, anti-inflammatory drugs inhibited enzyme activity most significantly: indomethacin (9.0 x 10(-3) mol l-1) decreased the phospholipase-A2 activity to one- tenth. The weak inhibitory effect could also be demonstrated using a lower concentration of 2 x 10(-5) mol l-1, which can be achieved after intravenous administration of 50 mg of this drug. The other drugs inhibited the enzyme activity at concentrations higher than those achieved after intravenous injections in clinical use. Diclofenac (3.1 x 10(-2) mol l-1) reduced the phospholipase-A2 activity by 93%, ketoprofen (2.0 x 10(-2) mol l-1) or chlorpromazine (1.4 x 10(-2) mol l-1) by 90%, tobramycin (1.7 x 10(-2) mol l-1) by 84%, doxycycline (9.0 x 10(-3) mol l-1) by 61%, dexamethasone (1.7 x 10(-3) mol l-1) by 62%, methylprednisolone (3.8 x 10(-2) mol l-1) by 50%, and pindolol (1.0 x 10(-4) mol l-1) by 59%. A weak inhibition of phospholipase-A2 activity was demonstrated by betamethasone, bupivacaine, digoxin, hydrocortisone, lidocaine, metoprolol, propranolol, and vancomycin. Indomethacin proved the most potent of the tested agents in inhibiting phospholipase-A2 activity in serum from patients with acute pancreatitis and should be further studied in vivo.

Quality of life in pre-adolescence: a 17-dimensional health-related measure (17D)

Although interest in the health-related quality of life (HRQOL) of children has increased in the last years, validated methods for assessing the HRQOL- and especially the perceived HRQOL-of children have been missing. We introduced a 17-dimensional, illustrated, generic measure of perceived HRQOL (17D) for pre-adolescents, and demonstrated its application to three populations of children aged 8-11 years: (1) 244 normal schoolchildren; (2) 22 patients surviving organ transplantation and (3) 10 patients with genetic skeletal dysplasias. The HRQOL scores and profiles of the patients differed significantly according to the diagnosis, giving support to its construct validity. The reliability of the measure was high: its repeatability coefficient was 95%. As a structured interview of 20-30 minutes, the measurement burden is reasonable. We conclude that the assessment of quality of life of pre-adolescents can and should be based on data collected from the children themselves. Our initial experience indicates that 17D is comprehensive, reliable, and valid.

Health-related quality of life of adults surviving malignancies in childhood

While sophisticated data on specific problems are available, very little is known about the overall quality of life of long-term survivors of malignancies in childhood. We used a previously validated 15-dimensional questionnaire to examine the perceived health-related quality of life of 168 survivors, currently aged 16-35 years, who had been treated for a malignancy at a single institution between 1961 and 1993. All had been off therapy for at least 1 year (median, 12 years). In statistical terms, the quality of life score of the survivors was significantly better than that of 129 normal controls [0.966 versus 0.941 (theoretical maximum 1), respectively; P < 0.001]; however, a difference of this magnitude is most likely not clinically significant. There were no associations between original diagnosis and present quality of life, but the numbers in each diagnostic group were small. The survivors reported significantly better levels of vitality, distress, depression, discomfort, elimination and sleeping dimensions than the controls. Although we are presently not able to identify all the contributing factors, we speculate that the high perceived quality of life of long-term survivors of childhood malignancies is at least in part a consequence of denial mechanisms which compensate or even overcompensate the objectively measurable late effects of childhood cancer.

Quality of life in early adolescence: a sixteen-dimensional health-related measure (16D)

While data on the health-related quality of life (HRQOL) of adults are accumulating, very little is known about the HRQOL--and especially the perceived HRQOL--of children. In our study we introduced a 16-dimensional, generic self-assessment measure of HRQOL (16D) for early adolescents, and demonstrated its use with four populations of children aged 12-15: (1) 239 normal schoolchildren, (2) patients waiting for organ transplantation (n = 5), (3) patients with genetic skeletal dysplasias (n = 19), and (4) patients with epilepsy (n = 32). The HRQOL profiles of the patients differed significantly according to the diagnosis, giving support to its construct validity. The reliability of the measure was high: its repeatability coefficient was 91%. The quality of life ratings of the healthy boys and their parents differed on the dimensions of distress, vitality, speech, mental function, and discomfort and symptoms (p < 0.05). In addition, there were significant differences in the health-related valuations between the girls, boys and their parents. We conclude that the assessment of quality of life of adolescents should be based on data collected from the adolescents themselves. Further, the 16D is so far the only generic HRQOL measure designed specifically for this purpose. It is capable of differentiating the HRQOL of healthy adolescents as well as patients with various diagnoses. Our experience also indicates that it is easy to use, yet it seems comprehensive, reliable, and valid.

Facilitation of experimental allergic encephalomyelitis by irradiation and virus infection: role of inflammatory cells

Infection with an avirulent strain of Semliki Forest virus (SFV-A7) facilitates the development of experimental allergic encephalomyelitis (EAE) in a genetically resistant BALB/c mouse strain. Irradiation which is necessary for EAE induction caused a decrease in the total number of lymphocytes and an increase in CD4+/CD8+ T cell ratio in the spleen of BALB/c mice. EAE induction increased the ratio further until clinical and histological signs of EAE appeared. Entry of perivascular CD4+ and CD8+ cells preceded the onset of clinical signs and the appearance of MAC-1+ cells in the central nervous system (CNS). In the acute phase of EAE, cellular infiltrates, which were sparse, consisted mainly of MAC-1+ cells and a few CD4+ and CD8+ cells. Inflammatory cells gradually disappeared during the recovery phase. SFV-A7 infection after irradiation and EAE induction did not significantly change the CD4+/CD8+ ratio in the spleen or in the CNS infiltrates but enhanced the entry of inflammatory cell into the CNS. Similar perivascular cell influx was also seen in untreated mice infected with SFV-A7. We conclude that observed rapid reduction of splenic mononuclear cells and increase of the CD4+/CD8+ T cell ratio caused by irradiation prior EAE induction are early crucial events in disease induction in this resistant strain of mice. SFV-A7 infection, which further facilitates the development of EAE, does not induce immunoregulatory changes but provides its effect by enhancing the entry of inflammatory cells into the CNS. The combination of these two mechanisms thus effectively breaks the natural resistance against EAE in this genetically resistant mouse strain.

CRIB and SNAP: assessing the risk of death for preterm neonates

The performance of three scoring systems for assessing mortality risk for neonates--clinical risk index for babies (CRIB), score for neonatal acute physiology (SNAP), and SNAP's perinatal extension (SNAP-PE)--were tested in the same set of patients. In 222 neonates weighing less than 1500 g at birth, CRIB scores were significantly better for assessing mortality risk than SNAP (p = 0.017) or SNAP-PE (p < 0.001), areas under receiver operating characteristic curves being 0.89 (SE 0.02), 0.82 (0.03), and 0.79 (0.03), respectively. Male sex was independently associated with poor prognosis after taking the CRIB score into account with a risk ratio of 2.75. We conclude that CRIB is the most useful score for comparing the performance of neonatal intensive-care units. New treatment methods, however, may require modifications to the system.

Early effects of the self-reinforced PGA implant on a growing bone: an experimental study on growing rats

The purpose of the study was to investigate the immediate/early effects of a bioabsorbable implant on a growing bone and monitor the strength retention. Fifty-eight rats were used as experimental animals. In 29 animals a 1.1 mm self-reinforced (SR-PGA) polyglycolic acid implant was placed through a transphyseal drill channel up to the diaphysis of the femur. In another 29 rats similar implants were placed in both femora and in the dorsal subcutis. After a follow-up time of 1-28 days a histologic and a roentgenographic analysis of the femora was undertaken and the shear and bending strengths of the removed implants in the other group were measured. The implant was broken at the plane of the growth plate by 21 days. No permanent growth disturbance occurred in the operated femora compared to the control side. The SR-PGA implants lost a substantial part of their mechanical strength in 2 weeks.

Absorbable membranes for bone repair: an experimental study on rabbits

To study the use of absorbable self-reinforced polyglycolide (SR-PGA) membranes for bone repair, distal femoral metaphyseal osteotomies were created in 10 rabbits and diaphyseal osteotomies in five. Osteotomies were fixed with intramedullary PLLA rods and PGA membranes were applied over the osteotomy. They were followed up for 6, 12 and 24 weeks. Radiography, histology, microradiography and oxytetracycline fluorescence labelling studies were used to evaluate the outcome. Healing occurred without complications in the metaphyseal series while failure was recorded in the diaphyseal series. In metaphyseal osteotomies, new bone formation was seen medially (on the side of PGA membrane), more proximal and medial to the membrane than at the inlet of osteotomy.

Immunologic studies of nonunited fractures

We studied tissue samples of noninfected delayed union or nonunion of diaphyseal bones in 10 patients immunopathologically and neuroimmunologically 4 to 25 months after the primary injury. Samples mostly consisted of vascularized connective tissue of varying density with the proline-4-hydroxylase-containing fibroblast as the major cell type. Most inflammatory cells were CD4 T-lymphocytes and their number was always twice that of the CD8 positive cells. Staining for CD11b positive monocyte/macrophages showed in all samples positive cells scattered in the connective tissue stroma with perivascular enrichments. Mast cells were absent or very rare. Our findings suggest that delayed union and nonunion tissue consists of vascularized connective tissue, which mostly contains 5B5 fibroblasts, CD11b macrophages and vascular endothelial cells with only few immigrant recently recruited monocytes or lymphoid cells. Almost all resident cells seem to be involved in tissue remodeling as suggested by their content of fibroblast-type MMP-1 and its proteolytic activator MMP-3 or stromelysin. The most striking finding was the paucity or total lack of peripheral innervation, which may have to do with the nonunion of the fracture.

Fixation of diaphyseal femoral osteotomy with self-reinforced biodegradable intramedullary implants: an experimental study on growing dogs

Polyglycolic acid (PGA) was investigated for use as a biodegradable suture and fixation material for the repair of soft and osseous tissue. Self-reinforced (SR-) PGA has been used successfully since 1984 as an internal fixation material for fixation of cancellous bone fractures. The purpose of this study was to examine the possible usefulness of an intramedullary SR-PGA rod in the fixation of femoral shaft osteotomy in the growing dog. Osteotomy of the right femur was made in 14 Beagle dogs at 12 weeks of age. After accurate reduction, the osteotomy was fixed with an intramedullary 45 x 60 mm SR-PGA rod. The intramedullary SR-PGA rod provided sufficient stability for healing of a femoral shaft osteotomy in the growing dog and did not cause any significant growth disturbance.

Radiological evaluation of the acromioclavicular joint

X-ray measurement of the acromioclavicular (AC) joint may cause difficulties because of different projections and the lack of a reproducible measurement. In order to find the ideal measurement to estimate the state of the AC joint, 28 healthy adult volunteers were X-rayed. The least vulnerable measurement for errors in projection was the distance between the coracoid process and the upper part of the clavicle. The effect of stress was evaluated; the range of normal AC joint laxity was determined as 3 mm.

A histomorphological study on self-reinforced polyglycolide (SR-PGA) osteosynthesis implants coated with slowly absorbable polymers

A total of 150 osteotomies of rabbits' distal femur were fixed with absorbable self-reinforced polyglycolide (SR-PGA) rods coated with slowly absorbable polymers. In order to reduce the degradation rate of the SR-PGA construction rods were coated with n-butyl-2-cyanoacrylate, polydioxanone (PDS), poly-beta-hydroxybutyrate (PHBA), or poly-l-lactide (PLLA). Biocompatibility and the rate of biodegradation were evaluated in histological, histomorphometric, microradiographic, and oxytetracycline labeling studies. PDS, PHBA, and PLLA coatings showed good biocompatibility although there were scattered fluid accumulations around the rod in each group. Cyanoacrylate coating seemed to inhibit cartilage regeneration and cause the formation of considerable amount of connective tissue around the implant. The PGA core of the rod had totally degraded in 24 to 36 weeks in each coating group. Cyanoacrylate and PDS coatings were not detectable after 6 weeks while PHBA and PLLA coatings were still observed after 48 weeks. There were five (14%) non-unions in the cyanoacrylate coating group, one (3%) in the PHBA coating group caused by a purulent infection and none in the PDS and PLLA coating groups.

Phospholipase A2 activity and concentration in several body fluids in patients with acute pancreatitis

According to recent studies, phospholipase A2 (PLA2) may be an important factor in the pathogenesis and pathophysiology of acute pancreatitis. Increased serum PLA2 activities and concentrations have been measured in patients with acute pancreatitis. Serum PLA2 activities have been shown to correlate with the severity and prognosis of the disease. To study the different methods of PLA2 determination, we measured the PLA2 activity by means of an isotopic assay method and the concentration by a radioimmunologic method in several body fluids of 52 consecutive patients with acute pancreatitis. PLA2 activity and concentration were detected in all of the patient body fluids. The serum PLA2 activities were 2.5-fold higher (mean +/- SD, 7.6 +/- 6.0) than normal activities, and the concentrations were 9.6-fold higher (mean +/- SD, 41 +/- 88). The enzyme activities and concentrations correlated well in ascites, fluids from the pleural cavity, and peritoneal lavation and poorly in serum, urine, and fluid from pancreatic pseudocyst.

Comparison of in vitro hydrolysis, subcutaneous and intramedullary implantation to evaluate the strength retention of absorbable osteosynthesis implants

To evaluate the behaviour of mechanical properties of absorbable osteosynthesis implants in vivo, the strength retention of self-reinforced polyglycolide rods in distilled water at 37 degrees C in the subcutis and femoral medullary cavity of the rabbit was investigated. The self-reinforced polyglycolide rods lost their strength significantly faster in vivo than in vitro. The strength loss of the self-reinforced polyglycolide rods was only slightly faster in the medullary cavity than in the subcutis. As the removal of the implants from the medullary cavity became difficult 5-6 wk after implantation, it is suggested that subcutaneous implantation would be a suitable method to evaluate the strength retention of absorbable osteosynthesis implants.

Ankle fractures treated using biodegradable internal fixation

In order to reduce the resources needed for the removal of metallic fixation devices in fracture treatment, absorbable implants of biodegradable synthetic polymers were developed using self-reinforced lactide-glycolide copolymer and polyglycolide. In a prospective study 102 patients with displaced unimalleolar or bimalleolar fractures of the ankle were managed using internal fixation devices consisting of cylindrical biodegradable implants 3.2 or 4.5 mm in diameter and 50 or 70 mm in length. After open reduction of the fracture a channel was drilled from the tip of the malleolus into the cancellous bone through the fracture surfaces. A biodegradable rod of the same diameter was then tapped into the drill channel to fix the fracture. Postoperatively, the ankle was immobilized by a plaster cast for six weeks. An anatomic initial reduction was achieved in 93 patients (91%). A slight secondary displacement occurred in four patients. In six patients a sinus formation yielding remnants of the degrading implant was seen two to four months after the operation. This minor complication did not influence the union of the fracture or functional recovery. At the one-year follow-up examination there was no change in the ability to participate in sports and other physical activities in 89 patients (87%). The biodegradable fixation method is now the routine approach of the department in treating displaced unimalleolar and bimalleolar ankle fractures. New clinical applications for the implants are under trial.

Behavior of plasma phospholipase A2 activity in experimental acute pancreatitis according to diet

The effects of standard, fat-rich, protein-rich, and carbohydrate-rich diets combined with either long-term ethanol ingestion or tap water ingestion on the behavior of plasma phospholipase A2 activity during experimental acute pancreatitis were studied in rats. Phospholipase A2 activity was compared with amylase activity in the plasma. Three hundred eighty-four male Wistar rats were randomized into eight groups receiving different diets with either 15 percent (volume for volume) ethanol or tap water for 12 weeks. Thereafter, all groups were subdivided into control (intact) and pancreatitis subgroups. Pancreatitis was induced by retrograde bile infusion into the pancreatic ducts. Sampling was performed 24 hours after induction in the surviving rats. Ethanol ingestion alone and in combination with the fat-rich diet increased the mortality rate (p less than 0.05), whereas the lowest mortality rate was observed in the carbohydrate-rich diet and water and the carbohydrate-rich diet and ethanol groups. Plasma phospholipase A2 activity increased in most of the groups, but it correlated with the mortality rate in the standard diet group only. Plasma amylase activity increased significantly in all groups, but did not correlate with mortality rate. Plasma phospholipase A2 activity seems to be dependent on diet in experimental acute pancreatitis in rats. Plasma amylase activity may be less affected by the dietary composition, but the lack of a correlation with mortality makes it unreliable as a parameter of severity in experimental acute pancreatitis.

Aseptic necrosis of the femoral head during pregnancy

Two patients are presented with rare aseptic osteonecrosis of the femoral head appearing during the last trimester of pregnancy. Both patients suffered from increasing pain in one hip joint, beginning about one month before parturition. Radiographs demonstrated local osteoporotic changes of the femoral head on the painful side. Needle aspiration of the hip joint yielded a scant amount of clear, sterile synovial fluid and gave prompt relief of pain in both cases. The patients' history did not demonstrate any predisposing factors to osteonecrosis other than pregnancy. Treatment comprised omission of weight-bearing on the affected lower extremity for a month or two. The patients had completely recovered one year postpartum, and radiographs were normal.

Biodegradable implants in the fixation of physeal fractures in cats and dogs

In a preclinical and a clinical study physeal fractures of cats and dogs were fixated with biodegradable implants. The preclinical part consisted of 4 cats with experimental physeal fractures of the distal femurs and the clinical part of 6 cats and 8 dogs with different physeal fractures. All fractures were fixated with selfreinforced polyglycolic acid (PGA) implants of different sizes. No external support was applied after the fixation. All cats and dogs used their operated legs during the first postoperative week and they could walk without lameness in 6 weeks. The fracture healed without delay or malformations. The retardations of the growth of the physeal regions were considered minimal.

A simple isotopic assay method for human serum phospholipase A2 activity

An assay using 2-(1-14C)palmitoyl-labelled dipalmitoyl phosphatidylcholine substrate for the determination of serum phospholipase A2 (PLA2) activity is described and validated. The rapid determination of the enzyme activity is enabled by a simple liquid-liquid partition system to replace the laborious thin-layer chromatography used in earlier studies. The PLA2 activity of human pancreatic juice was used for the optimization of the assay. Interference by serum phospholipids can be avoided by using 10 microliter aliquots of serum in the assay, whereas larger amounts caused a progressive inhibition of the enzyme activity. Virtually no enzyme activity is determined in serum from normal healthy subjects (range from 1.2 to 3.0 IU/l). In acute haemorrhagic pancreatitis the PLA2 activity is markedly elevated (range from 10.7 to 42.0 IU/l). Due to the simple extraction of the reaction products the results can be obtained the same day. Therefore, the assay can conveniently be used for the rapid clinical identification of subjects with acute haemorrhagic pancreatitis.

Biodegradable internal fixation for malleolar fractures. A prospective randomised trial

Fifty-six patients with displaced malleolar fractures had open reduction and fixation of the fracture fragments using, by random selection, either biodegradable implants or metal AO plates and screws. The cylindrical biodegradable implants were made of polylactide-glycolide copolymer (polyglactin 910). The complications, radiographic results and functional recovery were studied prospectively. After follow-up of at least one year, no significant differences emerged in the complication rate or in the results of treatment between the two methods of fixation. Because of the advantage of avoiding the need to remove metal fixation after union, we now use biodegradable internal fixation routinely to treat displaced malleolar fractures.

The use of neuroleptanaesthesia for experimental orthopaedic surgery in the rabbit

The anaesthesia of the rabbit used as a laboratory animal in experimental orthopaedics may present problems. The anaesthetic method should be easy and safe. Preferably it should not be expensive and should not include sophisticated devices. The anaesthesia has to include all the components: complete analgesia, muscular relaxation, and sedation. The application of the anaesthesia should not cause anxiety and pain to the animal, e.g. rigorous restraint has to be avoided.

Long-term ethanol ingestion causes an increase of phospholipase A2 activity in acute experimental pancreatitis in rats

Alcohol is recognized as one etiological factor in pancreatitis and according to recent studies, phospholipase A2 (PLA2) may be an important factor in the pathogenesis of this disease. However, the effect of chronic ethanol ingestion on PLA2 activity has not been studied in pancreatitis. To clarify the possible relation of these two factors 48 male Wistar rats received 15% (v/v) ethanol in drinking water for 12 weeks and 48 rats served as controls drinking tap water. Blood samples were collected from the control animals by puncturing the abdominal aorta. Experimental pancreatitis was induced by intraductal retrograde infusion of normal rat bile and blood samples collected 24 hr after the infusion. PLA2 activities in the plasma were measured by using the substrate with a 3H-labeled fatty acid in position 2. PLA2 activities in the control group were 11.2 +/- 1.3 (mean +/- SE) nmole/ml/min and 21.7 +/- 3.5 twenty-four hours later (P less than 0.05). In alcoholic rats the activities were 11.1 +/- 1.4 and 54.0 +/- 10.3, respectively (P less than 0.003). The increase of the activities was greater in alcoholic rats and the difference between the groups statistically significant (P less than 0.025). The mortality rate was 4.2% among the control animals and 29.2% in the alcoholic groups (P less than 0.026). The results of this study suggest that chronic alcohol ingestion makes the pancreas vulnerable to severe pancreatitis with high mortality. This is associated with significantly increased activities of PLA2.

Hip arthroplasty for alkaptonuric ochronosis. A case report

Ochronotic arthropathy is present in about one third of the patients with alkaptonuria. The large joints, as well as the spinal column, are affected. In a typical case with a grave classic ochronotic arthro- and spondylopathy, arthroplasties of the hips greatly increased the patient's physical activity.