Factor Xa (FXa) inhibitor from the nymphs of the camel tick Hyalomma dromedarii

An inhibitor of factor Xa (FXa) was isolated from the nymphs of the camel tick Hyalomma dromedarii by a combination of chromatography on DEAE-cellulose and Sephacryl S-300 columns. The isolated nymphal FXa inhibitor turned out to be a homogenous preparation of a single polypeptide chain (15 kDa) as judged by both the native and denatured SDS-PAGE. Its pI value ranged from 7.7 to 7.9. The inhibitor is a potent anticoagulant since it prolonged both the activated partial thromboplastin time (APTT) and the prothrombin time (PT) of the camel plasma in a concentration-dependent manner. Its activity was threefold lower toward thrombin than FXa, but it did not inhibit any of the proteases; trypsin, alpha-chymotrypsin, papain, pepsin and subtilisin. The inhibitor binds at two sites on FXa uncompetitively with an inhibition constant (K(i)) value of 134 nM.

Population-based health principles in medical and public health practice

Traditionally, medical education, research, and practice have focused on the care of the individual but an increasing emphasis on the care of populations has raised awareness among academic medical centers, integrated delivery systems, and managed care organizations of the value of embracing population-based health principles. Five principles are relevant in this regard: a community perspective, a clinical epidemiology perspective, evidence-based practice, an emphasis on outcomes, and an emphasis on prevention. This article describes these interrelated concepts together with specific strategies to effect implementation. Widespread awareness and adoption of these principles will have a profound impact on medical and public health education, practice, and ultimately the public's health.

Risks of fracture of Björk-Shiley 60 degree convexo-concave prosthetic heart valves: long-term cohort follow up in the UK, Netherlands and USA

BACKGROUND AND AIM OF THE STUDY

Approximately 82,000 Björk-Shiley convexo-concave (BSCC) 60 degree prosthetic heart valves were implanted in patients worldwide between 1979 and 1986. Outlet strut fractures (OSF) of some of the valves were first reported shortly after their introduction. Here, the determinants of OSF are examined, and the between-country variation and long-term risk are assessed.

METHODS

Cohorts of patients in the UK, Netherlands and USA with 15,770 BSCC 60 degree heart valves were followed up to 18 years for the occurrence of OSF.

RESULTS

Crude rates of OSF were highest in the UK (0.18% per year), intermediate in the Netherlands (0.13%), and lowest in the USA (0.06%), although risk factor adjustment reduced the inter-country differences. Furthermore, in the UK and Netherlands, OSF rates (particularly for mitral valves) declined with time since implantation, and between-country differences were considerably diminished 10 or more years post implantation. The risk of OSF decreased steadily with advancing patient age. Fracture rates were lower among women than men, and also varied significantly with valve size and position and OSF status of other valves in the same shoporder.

CONCLUSION

This long-term follow up of BSCC 60 degree heart valve patients indicates that risk factors for valve fracture are generally similar in the UK, Netherlands and USA. It also identifies a strong association between fracture risk and age, newly reveals gender-related differences, and shows that the risk of valve fracture persisted, albeit at a reduced rate, into the 1990s.

Isolation and properties of two forms of thrombin inhibitor from the nymphs of the camel tick Hyalomma dromedarii (Acari: Ixodidae)

Two forms of the nymphal thrombin inhibitors (NTI) 3.2 kDa and 14.9 kDa were purified by chromatography on CM-cellulose. Sephacryl S-300 and Sephadex G-50 columns and designated NTI- 1 and NTI-2 respectively. The NTI-2 turned out to be homogenous monomeric protein in both native-PAGE and denatured SDS-PAGE with M(r) value of 14.9 kDa approximately and its pI value ranged from 7.2 to 7.5. The NTI-1 and NTI-2 displayed anticoagulant activity since they prolonged both the activated partial thromboplastin time (APTT) and the prothrombin time (PT) of the camel plasma in a concentration-dependent manner. The potency of NTI-I toward thrombin was 5-fold higher than that toward FXa, while NTI-2 was 3-fold active toward FXa than thrombin. However, both of them did not inhibit any of the other examined proteases. The types of inhibition of thrombin by NTI-1 and NTI-2 were non-competitive and competitive with inhibition constants (Ki) values of 11.7 microM and 211 nM respectively. One binding site was deduced on thrombin for each inhibitor.

Molecular dating of senile plaques in the brains of individuals with Down syndrome and in aged dogs

beta-Amyloid (Abeta) is a constituent of senile plaques found with increasing age in individuals with Down syndrome (DS) and in the canine model of aging. Sections of DS and dog brain were immunostained using an affinity-purified polyclonal antibody for a posttranslationally modified Abeta with a racemized aspartate at position 7 (d7C16). The immunostaining characteristics of d7C16 Abeta in DS and dog brain indicate that it is present in all plaque subtypes, including the thioflavin-S-negative diffuse plaques that develop with age in dogs. The youngest DS case exhibited weak immunolabeling for d7C16 but the extent of d7C16-positive plaques increased with age. In addition, d7C16-positive plaques were initially found in clusters in the superficial layers of the frontal and entorhinal cortex but, with advancing age, increasing numbers appeared in deeper layers, suggesting a progression of Abeta deposition from superficial to deeper cortical layers. Ultrastructural studies in DS brain were confirmed using perfused dog brain and provided consistent results; thioflavin-S-negative diffuse plaques consist of fibrillar Abeta and racemized Abeta is associated with thicker and more highly interwoven fibrils than nonracemized Abeta. The use of antibodies to modified forms of the Abeta protein should provide insight into the progression of plaque pathology in DS and Alzheimer's disease brain.

The contributions of erosion, swelling, and porosity to theophylline release kinetics from Cissus populnea polymer matrices

The variable factors of erosion rate, swelling rate, and porosity were used in studying the release patterns of theophylline from our Cissus populnea polymer (CPP) matrices under the different factor combinations given by a simple 2n factorial experimental design. The zero-order slopes and correlation coefficients representing release rate and linearity, respectively, as obtained from both the nonsteady state and steady state were statistically treated. It appears that the nonsteady-state analysis is more suitable for studying the effects of individual factors, while the steady-state analysis appears more suitable for studying interaction effects of the factors. The study also showed that erosion is the main mechanism by which theophylline is released from the matrices, while swelling is responsible for maintaining linearity in the zero-order release curves. A careful examination of the statistical results shows some functional relationships between the factors, which should be considered in designing more detailed factorial experiments to enable the establishment of equation models for predicting the release profile of theophylline from our CPP matrices under any given dissolution condition.

Attenuation of fission neutrons by some hydrogeneous shield materials and the exponential dependence of the attenuated total neutron dose rate on the shield thickness

This work deals with the attenuation of fission neutrons by some hydrogeneous shield materials. The attenuated fission neutrons are described by the energy groups (fast, epithermal and thermal). The exponential decrease in the fast flux is represented by the removal cross section concept. Each of the epithermal and thermal fluxes is expressed using the diffusion equation including a pair of arbitrary constants to be determined using the corresponding boundary conditions. The solution obtained for the required arbitrary constants is then approximated in a simplified form such that it may easily replace the corresponding exact solution. The attenuation values, by which the neutron dose rate distributions are exponentially decreased through certain thicknesses are also determined for the given materials. They are compared to the corresponding experimental and theoretical data. The results obtained for the total neutron dose rate distributions in terms of a suitable range of layer thicknesses are then used to determine--for each material--an average value for the total neutron dose rate representing the exponential decrease during passage through the considered range of layer thicknesses.

Traffic of the tick embryo basic protein during embryogenesis of the camel tick Hyalomma dromedarii (Acari: Ixodidae)

The tick embryo basic protein (TEBP) is present in the nucleus as a counterpart of histones at early embryonic stages of the tick Hyalomma dromedarii. The sharp drop in the TEBP nuclear level and elimination of the N-terminal dipeptide (leucine-serine) between days 12 and 15 after oviposition suggested the transport of TEBP to the cytoplasm for protein turnover. The traffic of TEBP during tick embryogenesis was examined. The level of TEBP was detected in the cytoplasm from the different embryonic stages by the established enzyme-linked immunosorbent assay (ELISA) and confirmed by immunoblotting. At day 12, a 2-fold increase in the cytoplasmic TEBP level coincided with its decrease in the nucleus. This result indicates that TEBP starts to leave the nucleus for the cytoplasm at day 12. The changes in the cytoplasmic leucine aminopeptidase (LAP)-specific activity were followed during tick embryogenesis. The LAP activity started to increase at day 12 and reached its maximum level at day 21. The enzyme displayed an optimum pH between 7.5 and 8.8 and a K(m) value of 0.5 microM for leucine-p-nitroanilide. The involvement of the exopeptidase activity in the TEBP turnover after its translocation to the cytoplasm is discussed.

Magnetic resonance imaging relaxation times and gadolinium-DTPA relaxivity values in human cerebrospinal fluid

RATIONALE AND OBJECTIVES

This study was conducted to prove the feasibility of using cerebrospinal fluid (CSF) T1 and T2 measurements to assess the blood-brain barrier integrity in disease states not noted for focal blood-brain barrier disruption, such as Alzheimer's disease.

METHODS

T1 and T2 of human CSF samples were measured with and without gadolinium Gd-DTPA over a concentration range of 1.98 x 10(-3) to 6.32 mM, in a GE 1.5-T Signa scanner.

RESULTS

T1 and T2 of human CSF without Gd-DTPA were measured as 2.39 and 0.23 s. K1 and K2 were calculated as 6.25 and 6.74 mM(-1) s(-1). The lowest Gd-DTPA concentration with measurable T1 and T2 was 1.98 x 10(-3) mM. There is no statistically significant difference in T2 and K2 at different repetition times.

CONCLUSIONS

This work demonstrates that a single measurement of relaxation times after contrast-enhanced magnetic resonance imaging could be used to determine the Gd-DTPA concentration in CSF. It may thus be feasible, using this technique, to measure intersubject and intraregional variability in the quantity of Gd-DTPA transferred across the blood-brain barrier after intravenous injection of contrast agent.

Management after myocardial infarction: a controlled trial of the effect of group psychotherapy

A controlled clinical trial was conducted to determine the feasibility of offering group psychotherapy to post-myocardial infarction patients for one year, and to test its effects upon prognosis. Shortly after discharge from a coronary care unit, 118 patients were approximately equally allocated to therapy and control groups. The acceptance, the average attendance at the weekly sessions, and the drop-out rates per cent were 84, 69 and 15.5 respectively. No statistically significant changes were shown in the physiological and psychological factors. Favorable effects were suggested by survival experience, changes in social alienation, length of hospital stay and the patients' reported attitudes toward this form of therapy.

Sexually transmitted diseases in domestic expatriate workers in Jeddah, Saudi Arabia

This study was conducted to determine the sexually transmitted diseases in domestic expatriate workers (DEWs) screened for pre-employment in the general clinics of a teaching hospital. The study included 1648 domestic expatriate workers who were reviewed by a general practitioner, and who underwent serological tests for treponemal infections and human immunodeficiency virus (HIV). Screening for hepatitis B surface antigen (HBsAg) was also done routinely as part of the requirement of the pre-employment screening. The relative frequencies for syphilis and HIV were 23.8% and 19% respectively. HIV was detected more frequently in DEWs from Africa, and syphilis in DEWs from Indonesia and the Philippines, whereas HGsAg was more frequently detected in DEWs from the African subcontinent, and was significant among males (2.8%), compared to females (1.0%), where P7lt;0.05. These findings indicate that pre-employment screening is a viable means of identifying major STDs (venereal syphilis, HIV) and communicable diseases such as hepatitis B in the DEWs. It is recommended that stringent measures be adopted to prevent fraudulent reporting from laboratories and health care providers locally, and from the home country of the DEW.

Purification and characterization of a novel acid-soluble nuclear protein from developing embryos of the camel tick Hyalomma dromedarii (Acarina: Ixodidae)

A novel acid-soluble protein has been extracted from nuclei of developing embryos of H. dromedarii ticks and purified to homogeneity. This tick embryo basic protein (TEBP) was predominant during the cleavage stage of tick embryogenesis, whereas the complete set of histones was detectable at the late cleavage stage. The amount of TEBP reaches a maximum value at day 9 after oviposition. Thereafter, the original N-terminal dipeptide (leucine-serine) is eliminated. This coincides with the start of organogenesis. In spite of its low molecular mass, TEBP seems to be related to histone H1 in some properties such as solubility in perchloric acid and binding affinity to DNA. A task for the future will be to define the role of this protein as a counterpart of the histones for the genome organization during embryogenesis.

The injured cell: the role of the dendritic cell system as a sentinel receptor pathway

A major unresolved paradox in immunology remains: how do we avoid harm, despite the abundant opportunities for induction of immune responses against self-proteins? Here, Mohammad Ibrahim, Benjamin Chain and David Katz extend Janeway's proposed explanation, arguing that adaptive immune responses are initiated not only by conserved microbial products, but also by microenvironmental tissue injury. They suggest that the key step is local dendritic cell activation, followed by upregulation of T-cell costimulatory molecules on these cells, and migration, leading to antigen presentation.

Evaluation of early (5 to 6 hours) iodine 123 uptake for diagnosis and treatment planning in Graves' disease

BACKGROUND

Twenty-four-hour radioactive iodine uptake measurements necessitate extra visits and time delays in diagnostic confirmation of and therapy planning for hyperthyroid patients. We evaluated the early (5 to 6 hours) measurement of iodine 123 uptake (EU) to predict late (24 hours) uptake (LU) and assessed its value in the management of hyperthyroidism.

METHODS

We conducted a prospective study in 51 previously untreated hyperthyroid and 27 euthyroid patients (initial evaluation group). Patients underwent both 6- and 24-hour 123I uptake measurements. A subsequent 21 patients with Graves' disease (confirmation group) were evaluated in light of regression data generated in the initial evaluation group.

RESULTS

An EU value of greater than 20% had a sensitivity of 100%, a specificity of 96%, and a positive predictive value of 98% for the diagnosis of hyperthyroidism and was superior to the most predictive LU value (> 30%), which had a sensitivity of 98%, a specificity of 89%, and a positive predictive value of 94%, in distinguishing the hyperthyroid patients from euthyroid patients or those with subacute thyroiditis. Regression analysis revealed that the 24-hour uptake of the hyperthyroid patients could be predicted from the early measurement with the following formula: LU = 28.94 + 0.584 (EU). The measured EU of the confirmation group was used to calculate a predicted LU with use of this formula. Measured LU and predicted LU correlated well (r = .85, P < .001). Iodine 131 dose calculations were performed post hoc; LU calculated doses correlated with predicted LU doses (r = .91, P < .001). Mean dose differences were small.

CONCLUSIONS

The EU of 123I can replace 24-hour uptake measurements. Early uptake measurement is reliable and clinically useful for diagnosis confirmation and treatment planning in thyrotoxic patients.

Supercritical fluid extraction and gas chromatography/ion trap mass spectrometry of pentachloronitrobenzene pesticides in vegetables

An analytical approach using supercritical fluid extraction (SFE) followed by gas chromatography/ion trap mass spectrometry (GC/ITMS) was developed for the analysis of the fungicide pentachloronitrobenzene and several analogues in vegetables. The method was tested in the analysis of carrots, potatoes, green beans, celery, and radishes fortified with pentachloronitrobenzene, tetrachloronitrobenzene, pentachloroanisole, pentachlorothioanisole, pentachlorobenzene, hexachlorobenzene, and pentachloroaniline. An incurred carrot sample analyzed by the method was shown to contain hexachlorobenzene at 7 +/- 3 ng/g, which agreed with the concentration (8 +/- 4 ng/g) determined using a traditional solvent-based method. The SFE method consisted of the following steps: (1) homogenizing a 50 g vegetable sample and weighing a 3 g subsample; (2) mixing 2 g sorbent (Hydromatrix) with the subsample to absorb moisture and packing a 10 mL extraction vessel; (3) extracting with 40 mL CO2 at 200 atm, 40 degrees C, and a flow rate of 3 mL/min; and (4) collecting the extract on a 1 g alumina basic trap at 25 degrees C and flushing with 8 mL isooctane. Collection of the extract on alumina efficiently removed chlorophyll and other matrix interferences. GC/ITMS in the electron-impact mode confirmed and quantitated the analytes at concentrations as low as 1 ng/g.

Effect of disk maturation on diffusion of low-molecular-weight gadolinium complexes: an experimental study in rabbits

PURPOSE

To measure the rate of enhancement in immature intervertebral disks in comparison with that of mature disks after intravenous administration of gadolinium-containing contrast media.

METHODS

Four rabbits were imaged with MR for 120 minutes after the injection of gadopentetate dimeglumine, gadoteridol, or gadodiamide. Contrast enhancement was measured in the lumbar intervertebral disks on each image. The rate and magnitude of enhancement in the immature and mature disks were compared.

RESULTS

Contrast enhancement was detected in intervertebral disks with all three contrast media. Enhancement was significantly greater in immature than in mature animals.

CONCLUSION

Greater enhancement in immature disks is consistent with a lower concentration of fixed negative charges in the glycosaminoglycans of the disk.

Enhancement of intervertebral disks with gadolinium complexes: comparison of an ionic and a nonionic medium in an animal model

PURPOSE

To compare MR contrast enhancement of intervertebral disk tissue after intravenous administration of equimolar doses of an ionic and of a nonionic gadolinium complex.

METHODS

Contrast enhancement was measured on MR in lumbar intervertebral disks for 120 minutes after intravenous injection of gadoteridol or gadopentetate dimeglumine, 0.3 mmol/kg. MR studies were performed with each contrast medium in four rabbits. Contrast enhancement was measured in intervertebral disks as a function of time and contrast medium.

RESULTS

With both contrast media, enhancement of normal intervertebral disks was detected. Enhancement of disks was significantly greater with gadoteridol than with gadopentetate dimeglumine.

CONCLUSION

The enhancement of cartilage is influenced by the molecular structure of the gadolinium complex. The negative charge of gadopentetate dimeglumine may give it a slower rate of diffusion into disk cartilage than a nonionic complex.

In situ extracorporeal shock wave lithotripsy (ESWL) for the management of primary ureteric calculi in children

Lithotripsy was used to treat 19 children (3 to 16 years of age) with primary ureteric calculi. No attempts were made to mobilize the stones to the kidney. Stones were located in the upper ureter in seven patients, middle ureter in three, and lower ureter in nine. Stone size ranged from 5 to 25 mm (average, 10.4 mm). All treatments were performed in the outpatient unit. Two children required general anesthesia, and 17 received intravenous sedation. The mean amount of energy used was 17.8 kV, and the average number of shock waves was 5,489. Before commencement of lithotripsy, two patients needed ureteric catheterization, and two had placement of double pigtail catheters. Of the 18 children who had adequate follow-up, 17 (94.4%) were completely stone-free, without any complication. The authors conclude that in situ extracorporeal shock wave lithotripsy is a safe and effective method for the treatment of primary ureteric calculi in children.

In situ extracorporeal shock wave lithotripsy for primary ureteric calculi

OBJECTIVE

To determine the efficacy of the Lithostar lithotriptor for the in situ treatment of primary ureteric stones.

METHODS

We reviewed, retrospectively, our experience with 283 patients with primary ureteric stones treated with extracorporeal shock wave lithotripsy (ESWL) using the Lithostar lithotriptor. No attempts were made to manipulate the stones. The majority of the patients were treated using only intravenous analgesia. Auxiliary measures were used in 84 patients (29.6%). There were 112 patients (39.6%) with upper, 53 (18.7%) with middle, and 118 (41.7%) with lower ureteric stones.

RESULTS

A single ESWL session was needed for 200 patients (70.6%), two for 49 patients (17.3%), and more than two sessions for 34 patients (12%). Of the 248 patients who had adequate follow-up, 220 (88.7%) were stone free, 14 (5.65%) had some residual stone, while 14 (5.65%) patients failed to respond to the treatment. Patients' gender and body weight influenced the treatment and the clearance rate numerically without any statistical significance. The stone site was the most significant factor influencing the final result. Stones larger than 10 mm and the presence of hydronephrosis adversely affected the treatment.

CONCLUSIONS

In situ ESWL of ureteral stones with the Lithostar device is a convenient and efficient method of treating calculi within the whole length of the ureter without the need for any manipulation.

The role of non-adhesive T-cell-accessory cell interactions in the induction of T-cell proliferative hyporesponsiveness

We have suggested previously that induction of T-cell proliferative hyporesponsiveness is associated with a defective adhesive T-cell-antigen-presenting cell (APC) interaction. In the previous study, the hyporesponsiveness was allospecific, implying that a T-cell receptor-major histocompatibility complex (MHC) interaction had occurred. Therefore, we hypothesized that this type of non-adhesive T-cell-APC interaction might induce T-cell tolerance rather than activation. This hypothesis has now been tested further in the present study, using two experimental approaches. Firstly, L cells, which express a T-cell receptor ligand, i.e. MHC class II molecules, but lack the capacity to bind to T cells and do not express the crucial receptor/counter receptor lymphocyte function-associated antigen-1 (LFA-1)/intracellular adhesion molecule-1 (ICAM-1) pair, also induced non-allospecific T-cell proliferative hyporesponsiveness; this was not due to any direct inhibitory effect on the T cells. Secondly, monoclonal antibodies (mAb) directed to LFA-1 and ICAM-1 were used to disrupt T-cell-APC adhesion specifically, while allowing for T-cell receptor-MHC interaction to occur. The results of this new study suggest that the non-allospecific T-cell proliferative hyporesponsiveness induced was a function of direct T-cell inhibitory effects of these mAb. Taken together, these experiments add further evidence to support the notion that accessory cells which engage T-cell receptors without providing the necessary co-stimulatory signals induce T cells which are in a state of functional 'paralysis' with respect to the antigen which the T-cell receptor recognizes.

Contrast enhancement of normal intervertebral disks: time and dose dependence

PURPOSE

To determine the dose of contrast medium and the imaging strategy sufficient to detect diffusion of low-molecular-weight gadolinium-containing contrast media into normal intervertebral disks.

METHODS

In 11 rabbits, sequential MR images were obtained of the spine for 120 minutes after intravenous injection of gadopentetate dimeglumine in doses of 0.1 to 2.8 mmol/kg. Images were inspected for evidence of contrast enhancement. Signal intensity was measured and plotted as a function of time and dose.

RESULTS

Contrast enhancement was detected by inspection of images and by measurement in animals receiving doses of 0.3 mmol/kg and larger.

CONCLUSIONS

Diffusion of gadolinium-containing chelates into the intervertebral disk can be detected with clinically used doses of commercially available contrast medium. Therefore, with MR and a gadolinium-containing contrast medium, diffusion into intervertebral disks can be studied.