Modelling COVID-19 transmission in Africa: countrywise projections of total and severe infections under different lockdown scenarios

OBJECTIVES

As of 13 January 2021, there have been 3 113 963 confirmed cases of SARS-CoV-2 and 74 619 deaths across the African continent. Despite relatively lower numbers of cases initially, many African countries are now experiencing an exponential increase in case numbers. Estimates of the progression of disease and potential impact of different interventions are needed to inform policymaking decisions. Herein, we model the possible trajectory of SARS-CoV-2 in 52 African countries under different intervention scenarios.

DESIGN

We developed a compartmental model of SARS-CoV-2 transmission to estimate the COVID-19 case burden for all African countries while considering four scenarios: no intervention, moderate lockdown, hard lockdown and hard lockdown with continued restrictions once lockdown is lifted. We further analysed the potential impact of COVID-19 on vulnerable populations affected by HIV/AIDS and tuberculosis (TB).

RESULTS

In the absence of an intervention, the most populous countries had the highest peaks in active projected number of infections with Nigeria having an estimated 645 081 severe infections. The scenario with a hard lockdown and continued post-lockdown interventions to reduce transmission was the most efficacious strategy for delaying the time to the peak and reducing the number of cases. In South Africa, projected peak severe infections increase from 162 977 to 2 03 261, when vulnerable populations with HIV/AIDS and TB are included in the analysis.

CONCLUSION

The COVID-19 pandemic is rapidly spreading across the African continent. Estimates of the potential impact of interventions and burden of disease are essential for policymakers to make evidence-based decisions on the distribution of limited resources and to balance the economic costs of interventions with the potential for saving lives.

The non-invasive measurement of faecal immunoglobulin in African equids

Eco-immunological research is encumbered by a lack of basic research in a wild context and by the availability of few non-invasive tools to measure the internal state of wild animals. The recent development of an enzyme-linked immunosorbent assay for measuring immunoglobulins in faecal samples from Soay sheep prompted us to optimize such an assay to measure immunoglobulin A (IgA: an antibody associated with parasitic nematode fecundity) in faecal samples from equids. We measured total IgA in domestic donkeys, wild plains zebras, and wild Grevy's zebras sharing the same landscape in central Kenya over two field seasons. Attempts to measure anti-nematode IgA more specifically, using a homogenized extract from a mixture of excreted nematodes, failed to clear background. However, we found that total IgA positively correlated with strongyle nematode faecal egg counts (FECs) in donkeys sampled during the wetter field season - a time when the donkeys were in good condition. Further, this relationship appeared among donkeys with high body condition but not among those with low body condition. Time lags of 1–4 days introduced between IgA and FEC measurements in repeatedly sampled donkeys did not yield correlations, suggesting that IgA and FEC roughly tracked one another without much delay in the wet field season. Such a direct IgA-FEC relationship did not appear for zebras in either the wet or dry field season, possibly due to higher interindividual variation in body condition among the free-roaming zebras than in the donkeys. However, Grevy's zebras had higher overall levels of IgA than either plains zebras or donkeys, potentially associated with their reportedly lower FECs at the population level. Our results suggest that equids may mount an IgA response to nematode egg production when the host is in good condition and that equid species may differ in baseline levels of mucosal IgA.

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We optimized an immunosorbent assay to non-invasively measure total IgA in faeces from equids.

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IgA positively correlated with nematode faecal egg count (FEC) in donkeys in good body condition.

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IgA and FEC were not correlated in a dry year for donkeys or in any year for wild plains and Grevy's zebras.

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IgA may relate to FECs at the population level only when body condition is uniformly good.

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IgA was higher in Grevy's than plains zebras or donkeys, suggesting differences in immune strategy.

Who attempts suicide among medical students?

OBJECTIVE

To identify factors associated with a history of suicide attempt in medical students.

METHODS

A Web-based survey was sent out to a sample of medical students. A multi-predictor Poisson regression was performed to identify factors associated with a history of suicide attempt. In addition, an elastic net regularization was used to build a risk calculator to identify students at risk for attempted suicide.

RESULTS

A total of 4,840 participants were included in the study. Prevalence of suicide attempts in the sample was 8.94%. Risk factors associated with past suicide attempt in the multi-predictor Poisson regression were as follows: female gender (P < 0.001); homosexuality (P < 0.001); low income (P = 0.026); bullying by university peers (P = 0.006); childhood (P = 0.001) or adult (P = 0.001) trauma; family history of suicide (P = 0.005); suicidal ideation within the last month (P < 0.001); daily tobacco use (P = 0.037); and being at severe risk for alcohol abuse (P = 0.023). Our elastic net model performed well with an AUC of 0.83.

CONCLUSIONS

This study identifies a number of key factors associated with a history of suicide attempts among medical students. Future longitudinal studies should assess the causal relationship between these factors and suicide attempts. Additionally, these results demonstrate that current available data on suicide attempts among medical students can be used to develop an accurate risk algorithm.

Respiratory syncytial virus prevalence in children admitted to five Kenyan district hospitals: a cross-sectional study

Acute respiratory infections (ARIs) are a leading cause of under-five mortality globally. In Kenya, the reported prevalence of respiratory syncytial virus (RSV) infections in single-centre studies has varied widely. Our study sought to determine the prevalence of RSV infection in children admitted with ARI fulfilling the WHO criteria for bronchiolitis. This was a prospective cross-sectional prevalence study in five hospitals across central and highland Kenya from April to June 2015. Two hundred and thirty-four participants were enrolled. The overall RSV positive rate was 8.1%, which is lower than in previous Kenyan studies. RSV-positive cases were on average 5 months younger than RSV-negative cases.

[Long-term results of kyphoplasty with additive dorsal instrumentation of incomplete burst fractures of the thoracolumbar spine in the elderly]

BACKGROUND

To offer a correct treatment strategy for osteoporotic vertebral body fractures remains a huge challenge in modern spine surgery.

PATIENTS AND METHODS

In the years 2002 and 2003 5 patients with incomplete burst fractures (AO type A3.1) of the thoracolumbar spine were included in this study (4 men, 1 woman, average age: 62.6 years, follow-up rate: 100 %). All 5 were treated by kyphoplasty and additional dorsal bisegmental instrumentation. Unlike today, dorsal instrumentation was done without cement augmentation. Inclusion criteria were age above 60 years, an adequate trauma, and a fracture between thoracic body 11 and lumbar body 3. Data acquisition was performed prospectively before and after the operation, after 3, 6, 12, 18 months, and after 5 years, including visual analogue scale (VAS) spine score, spinal function score, X-ray examination or in cases of complaints or limited assessability a CT examination, and SF 36 score after 5 years. As comparison group, we used 4 patients, suffering the same fracture type with a similar fracture location (1 man, 3 women, average age: 67.3 years), who were treated with kyphoplasty alone during the same time period.

RESULTS

No clinically relevant intra- and postoperative complications were registered in our study group. The operative bisegmental kyphotic reduction was slightly higher in our study group. Afterwards the correction loss was 9.8° in our study group, exceeding the reduction by 3.6°, whereas the comparison group suffered from a correction loss of 11.8°, exceeding the operative reduction by 8.5°, respectively. These differences were not statistically significant. Similarly, no statistically significant differences were registered with respect of physical component summary (PSC), mental component summary (MSC) score and VAS spine score. Both groups had comparable PSC and MSC scores to a norm group of the same age.

CONCLUSION

After 5 years the therapy concept seems to be of low risk and not being associated with major complications. The PCS and MCS scores are comparable to a norm group of the same age. The correction loss exceeded the operative reduction marginally but turned out to be slightly lower compared to that of an isolated kyphoplasty.

FPGA-Based Pulse Pile-Up Correction With Energy and Timing Recovery

Modern field programmable gate arrays (FPGAs) are capable of performing complex discrete signal processing algorithms with clock rates well above 100 MHz. This, combined with FPGA's low expense, ease of use, and selected dedicated hardware make them an ideal technology for a data acquisition system for a positron emission tomography (PET) scanner. The University of Washington is producing a high-resolution, small-animal PET scanner that utilizes FPGAs as the core of the front-end electronics. For this scanner, functions that are typically performed in dedicated circuits, or offline, are being migrated to the FPGA. This will not only simplify the electronics, but the features of modern FPGAs can be utilized to add significant signal processing power to produce higher quality images. In this paper we report on an all-digital pulse pile-up correction algorithm that has been developed for the FPGA. The pile-up mitigation algorithm will allow the scanner to run at higher count rates without incurring large data losses due to the overlapping of scintillation signals. This correction technique utilizes a reference pulse to extract timing and energy information for most pile-up events. Using pulses acquired from a Zecotech Photonics MAPD-N with an LFS-3 scintillator, we show that good timing and energy information can be achieved in the presence of pile-up utilizing a moderate amount of FPGA resources.

[Recommendations for the treatment of thoracolumbar and lumbar spine injuries]

This paper gives recommendations for treatment of thoracolumbar and lumbar spine injuries. The recommendations are based on the experience of the involved spine surgeons, who are part of a study group of the "Deutsche Gesellschaft für Unfallchirurgie" and a review of the current literature. Basics of diagnostic, conservative, and operative therapy are demonstrated. Fractures are evaluated by using morphologic criteria like destruction of the vertebral body, fragment dislocation, narrowing of the spinal canal, and deviation from the individual physiologic profile. Deviations from the individual sagittal profile are described by using the monosegmental or bisegmental end plate angle. The recommendations are developed for acute traumatic fractures in patients without severe osteoporotic disease.

[Reconstruction after spinal fractures in the thoracolumbar region]

The morbidity of anterior approaches has significantly influenced the development of therapeutic concepts for the treatment of thoracolumbar spine fractures. Minimally-invasive techniques such as mini-open and endoscopic have enlarged the numbers of anterior reconstruction after spinal fractures in the thoracolumbar region. These minimally-invasive approaches have been facilitated by the development of special implants adapted to the new technique and to the local anatomical requirements.Two multi center studies in Germany (MCSI and II) showed the trend towards minimal invasive procedures and anterior approaches in the German speaking spine centers. Since the first report on thoracoscopic anterior procedures in Germany in 1997 a growing number of spine centers established this method. There is still no evidence based high level literature to substantiate a significant benefit for the patients by anatomical reduction and reconstruction of the anterior spinal column. However, there are some reports on better short outcomes in radiological parameters as well as better clinical results in 5 to 8 year follow-ups.The minimal invasive anterior approach seems to be advantageous for the patients by reducing significantly additive operation morbidity. It has become more important over the last two decades for anterior reconstruction after trauma and posttraumatic malalignment of the thoracolumbar spine.

Evolution of the Design of a Second Generation FireWire Based Data Acquisition System

Our laboratory has previously reported on the basic design concepts of an updated FireWire based data acquisition system for depth-of-interaction detector systems designed at the University of Washington. The new version of our data acquisition system leverages the capabilities of modern field programmable gate arrays (FPGA) and puts almost all functions into the FPGA, including the FireWire elements, the embedded processor, and pulse timing and integration. The design is centered around an acquisition node board (ANB) that includes 64 serial ADC channels, one high speed parallel ADC, FireWire 1394b support, the FPGA, a serial command bus and signal lines to support a rough coincidence window implementation to reject singles events from being sent on the FireWire bus. Adapter boards convert detector signals into differential paired signals to connect to the ANB. In this paper we discuss many of the design details, including steps taken to minimize the number of layers in the printed circuit board and to avoid skewing of parallel signals and unwanted bandwidth limitations.

FPGA-Based Pulse Pileup Correction

Modern Field Programmable Gate Arrays (FPGAs) are capable of performing complex discrete signal processing algorithms with clock rates above 100MHz. This combined with FPGA's low expense, ease of use, and selected dedicated hardware make them an ideal technology for a data acquisition system for a positron emission tomography (PET) scanner. The University of Washington is producing a high-resolution, small-animal PET scanner that utilizes FPGAs as the core of the front-end electronics. For this next generation scanner, functions that are typically performed in dedicated circuits, or offline, are being migrated to the FPGA. This will not only simplify the electronics, but the features of modern FPGAs can be utilizes to add significant signal processing power to produce higher resolution images. In this paper we report on an all-digital pulse pileup correction algorithm that is being developed for the FPGA. The pileup mitigation algorithm will allow the scanner to run at higher count rates without incurring large data losses due to the overlapping of scintillation signals. This correction technique utilizes a reference pulse to extract timing and energy information for most pileup events. Using pulses were acquired from a Zecotech Photonics MAPDN with an LFS-3 scintillator, we show that good timing and energy information can be achieved in the presence of pileup.

Value of MRI imaging prior to a kyphoplasty for osteoporotic insufficiency fractures

Previous studies have shown the safety and effectiveness of balloon kyphoplasty in the treatment of osteoporotic vertebral compression fractures (OVCFs). MRI and particularly the short tau inversion recovery (STIR) sequence are very sensitive for detecting vertebral edema as a result of fresh fractures or micro-fractures. Therefore, it has a great therapeutic relevance in differentiating vertebral deformities seen by conventional X-ray and CT scans. Although an MRI scan is expensive, to my knowledge no study has evaluated the benefits of preoperative MRI in evaluating a therapeutic plan for kyphoplasty. This is a prospective study evaluating the benefit of a preoperative MRI scan regarding changes of kyphoplasty therapy. Twenty-eight patients were included in this study. Twenty-four patients were treated by balloon kyphoplasty, in a total of 40 vertebral bodies. The mean age was 73 years. All patients suffered from OVCFs. As a first step, all patients got a CT scan. The individual therapeutic plan was then defined by the patients' history, complaints and the results of the CT scan. As far as all criteria for kyphoplasty were fulfilled, an MRI examination including the STIR sequences was performed preoperatively. The number of times a change was made in therapy as a result from the additional information from the MRI was then evaluated. By performing a preoperatively MRI examination, the therapy plan was changed in 16 out of 28 (57%) patients. Eight patients underwent additional levels of kyphoplasty at the same procedure. In five patients, lesions were found to be old fractures and therefore were not treated operatively. Two of these patients received no kyphoplasty at all. Another patient only a part of the originally intended levels was treated. The other two cases received a kyphoplasty at different vertebral levels, as these vertebral bodies showed signs of an acute fracture in the MRI scan. Additionally, an incidental diagnosis of carcinoma of the kidney was made in two patients. Kyphoplasty was deferred and they were referred for further evaluation. One patient was found to have an aortic aneurysm. Kyphoplasty was performed and after that the patient was referred in order to treat the aneurysm. This study confirms the diagnostic benefits of an MRI scan before performing a kyphoplasty. For 16 out of 28 patients, the therapeutic plan was changed because of the information obtained by preoperative MRI. Preoperative MRI helped to generate the correct surgical strategy, by demonstrating the correct location of injury and by detecting concomitant diseases.

[Spinal column injuries in sport: treatment strategies and clinical results]

BACKGROUND

The management of patients with sport-related injuries of the spine is a challenging issue with regard to the ability to resume former sport activities. The current study analyses the rate of resumption of sports participation after conservative and operative treatment.

METHODS

In a 2-year period, 96 patients with sport-related injuries of the thoracic and lumbar spine were included in this prospective study. Conservative (19%) or operative treatment (81%) was performed depending on the extent, severity and instability of the trauma. The reduction, the loss of reduction over time and the VAS and Odom scores were assessed. A questionnaire was included to estimate the rate of resumption of sports participation.

RESULTS

Of the patients 91% resumed sports participation and 9% had to abandon all sport activities mostly due to neurological deficits. Minor loss of correction was found in patients with 360 degrees short segment fusions and major loss was found after conservative treatment.

CONCLUSION

The current management of injuries of the spine effectuates a high rate of resumption of sports activity following conservative or operative treatment.

Design of a Second Generation Firewire Based Data Acquisition System for Small Animal PET Scanners

The University of Washington developed a Firewire based data acquisition system for the MiCES small animal PET scanner. Development work has continued on new imaging scanners that require more data channels and need to be able to operate within a MRI imaging system. To support these scanners, we have designed a new version of our data acquisition system that leverages the capabilities of modern field programmable gate arrays (FPGA). The new design preserves the basic approach of the original system, but puts almost all functions into the FPGA, including the Firewire elements, the embedded processor, and pulse timing and pulse integration. The design has been extended to support implementation of the position estimation and DOl algorithms developed for the cMiCE detector module. The design is centered around an acquisition node board (ANB) that includes 65 ADC channels, Firewire 1394b support, the FPGA, a serial command bus and signal lines to support a rough coincidence window implementation to reject singles events from being sent on the Firewire bus. Adapter boards convert detector signals into differential paired signals to connect to the ANB.

A convenient fluorometric method to study sulfur mustard-induced apoptosis in human epidermal keratinocytes monolayer microplate culture

Sulfur mustard [SM; bis-(2-chloroethyl) sulfide], which causes skin blistering or vesication [(1991). Histo- and cytopathology of acute epithelial lesions. In: Papirmeister, B., Feister, A. J., Robinson, S. I., Ford, R. D., eds. Medical Defense Against Mustard Gas: Toxic Mechanisms and Pharmacological Implications. Boca Raton: CRC Press, pp. 43-78.], is a chemical warfare agent as well as a potential terrorism agent. SM-induced skin blistering is believed to be due to epidermal-dermal detachment as a result of epidermal basal cell death via apoptosis and/or necrosis. Regarding the role of apoptosis in SM pathology in animal skin, the results obtained in several laboratories, including ours, suggest the following: 1) cell death due to SM begins via apoptosis that proceeds to necrosis via an apoptotic-necrotic continuum and 2) inhibiting apoptosis decreases SM-induced microvesication in vivo. To study the mechanisms of SM-induced apoptosis and its prevention in vitro, we have established a convenient fluorometric apoptosis assay using monolayer human epidermal keratinocytes (HEK) adaptable for multiwell plates (24-, 96-, or 384-well) and high-throughput applications. This assay allows replication and multiple types of experimental manipulation in sister cultures so that the apoptotic mechanisms and the effects of test compounds can be compared statistically. SM affects diverse cellular mechanisms, including endoplasmic reticulum (ER) Ca2+ homeostasis, mitochondrial functions, energy metabolism, and death receptors, each of which can independently trigger apoptosis. However, the biochemical pathway in any of these apoptotic mechanisms is characterized by a pathway-specific sequence of caspases, among which caspase-3 is a key member. Therefore, we exposed 80-90% confluent HEK cultures to SM and monitored apoptosis by measuring the fluorescence generated due to hydrolysis of a fluorogenic caspase-3 substrate (acetyl- or benzyl oxycarbonyl-Asp-Glu-Val-Asp-fluorochrome, also designated as AC-or Z-DEVD- fluorochrome) added to the assay medium. Fluorescence was measured using a plate reader. We used two types of substrates, one (Sigma-Aldrich, CASP-3-F) required cell disruption and the other (Beckman-Coulter CellProbe HT Caspase-3/7 Whole Cell Assay Kit) was cell permeable. The latter substrate was useful in experiments such as determining the time-course of apoptosis immediately following SM exposure without disruption (e.g., due to cell processing). In SM-exposed HEK, fluorescence generated from the fluorogenic caspase-3 substrate hydrolysis increased in a time (0-24 h) and concentration (0.05, 0.1, 0.15, 0.2, 0.3, 0.5 mM) dependent manner. SM caused maximum fluorescence at about 0.5 mM. However, at 2 mM SM, fluorescence decreased compared with 0.5 mM, which remains to be explained. Following 0.3 mM SM exposure, which is considered to be the in vitro equivalent of a vesicating dose in vivo (Smith, W. J., Sanders, K. M., Ruddle, S. E., Gross, C. L. (1993). Cytometric analysis of DNA changes induced by sulfur mustard. J. Toxicol.-Cut. Ocular Toxicol. 12(4):337-347.), a small fluorescence increase was observed at 6 to 8 h, which was markedly higher at 12 h. At 24 h, all SM concentrations increased fluorescence. Fluorescence increase due to SM was prevented 100% by a caspase-3-specific peptide inhibitor AC-DEVD-CHO (acetyl-Asp-Glu-Val-Asp-aldehyde, 0.1 mM), but less effectively by a general caspase inhibitor Z-VAD-FMK (benzyl oxycarbonyl-Val-Ala-Asp-fluoromethylketone, 0.01 mM), indicating that the fluorescence increase was due to caspase-3-mediated apoptosis. These results suggest potential applications of this method to study apoptosis mechanisms involving caspase-3 substrates and possibly those involving other caspase substrates.

Kyphoplastik im konventionellen und halboffenen Verfahren

Kyphoplasty is a young method which was developed for the minimally invasive augmentation of osteoporotic vertebral fractures. In contrast to vertebroplasty, the kyphoplasty technique allows an age-dependent fracture reduction through the inflation of a special balloon in the fractured cancellous bone of the vertebral body. The cancellous bone of the fracture zone is compressed by the balloon, so that a cavity remains in the vertebral body after removing the balloon, which is filled with highly viscous augmentation material. The reduced risk of serious complications, for example epidural leakage of augmentation material, justifies progressively expanding the indications for this technique to traumatic fractures with involvement of the posterior vertebral wall and neoplastic vertebral collapse due to osteolytic metastasis. Besides the indications for the conventional percutaneous approaches, the microsurgical interlaminary approach allows the use of kyphoplasty in more complex fractures involving compression of the neural structures. Kyphoplasty induces swift pain relief and allows rapid mobilisation of patients due to the immediate stabilisation of the affected vertebral bodies. Apart from the operative intervention, the medical treatment of the primary disease and the rehabilitation of the individual patient should be optimised through an interdisciplinary approach.

Increased insulin sensitivity and upregulation of insulin receptor, insulin receptor substrate (IRS)-1 and IRS-2 in liver of Ames dwarf mice

In the present study we have used hypopituitary Ames dwarf mice, which lack GH, prolactin and TSH, to investigate the consequences of the deficiency of these hormones on glucose homeostasis and on the initial components of the insulin signal transduction pathway in the liver. Ames dwarf mice displayed hypersensitivity to insulin since they maintained lower fasting glucose concentrations (73% of control values), had significantly reduced amounts of insulin (58% of control values), and exhibited an increased hypoglycemic response to exogenous insulin. Probably as a result of reduced insulin production, Ames dwarf mice displayed intolerance to glucose. The insulin-stimulated phosphorylation of the insulin receptor (IR) tended to be increased in the liver of Ames dwarf mice, while IR receptor protein content was increased by 38%. Insulin-stimulated phosphorylation of insulin receptor substrate (IRS)-1 and IRS-2 was increased by 61 and 72% respectively, while IRS-1 and IRS-2 protein levels were increased by 76 and 95%. The insulin-stimulated association of the p85 regulatory subunit of phosphatidylinositol (PI) 3-kinase with IRS-1 was increased by 28%, but unaltered with IRS-2. Interestingly, while the insulin-stimulated phosphotyrosine-derived PI 3-kinase activity was not changed, insulin-stimulated protein kinase B activation was increased by 41% in this tissue. These alterations may account for the insulin hypersensitivity exhibited by these animals. The present findings in long-lived Ames dwarf mice add to the evidence that insulin signaling is importantly related to the regulation of aging and life span.

Genes that prolong life: relationships of growth hormone and growth to aging and life span

Mutant mice with a combined deficiency of growth hormone (GH), prolactin, and thyrotropin, and knockout mice with GH resistance, live longer than their normal siblings. The extension of life span in these animals is very large (up to 65%), reproducible, and not limited to any particular genetic background or husbandry conditions. In addition to demonstrating that genes control aging in mammals, these findings suggest that GH actions, growth, and body size may have important roles in the determination of life span. We describe the key phenotypic characteristics of long-living mutant and knockout mice, with an emphasis on those characteristics that may be related to delayed aging in these animals. We also address the broader topic of the relationship between GH, growth, maturation, body size, and aging, and we attempt to reconcile the well-publicized antiaging action of GH with the evidence that suppression of GH release or action can prolong life.

Increased serum S100B protein in schizophrenia: a study in medication-free patients

S100B protein, a calcium binding protein produced and released by glial cells, has been used as a sensitive marker of brain damage. Previous studies have found alterations in peripheral S100B levels in schizophrenic patients on medication. We compared serum S100B levels of 20 medication-free DSM-IV schizophrenic patients and 20 age-gender matched healthy controls. Schizophrenic patients presented higher serum S100B levels (mean 0.120 ng/ml+/-S.D. 0.140) compared to controls (mean 0.066 ng/ml+/-S.D. 0.067; P=0.014) and there was a negative correlation with illness duration (r=-0.496, P=0.031). The results of this study indicate that serum S100B levels may be a state marker of a limited neurodegenerative process, particularly in the early course of schizophrenia or, at least, in a subgroup of schizophrenic patients.

Prolonged longevity of hypopituitary dwarf mice

In two types of mutant dwarf mice, congenital deficiencies in pituitary function are associated with remarkably increased life expectancy. In this review, we will describe the key phenotypic characteristics of these animals, the evidence that they exhibit delayed aging, and the mechanisms that are suspected to account for their prolonged longevity.

Characterization of a human pancreatic secretory trypsin inhibitor mutant binding to Legionella pneumophila as determined by a quartz crystal microbalance

We describe the isolation from a large phagemid library of a human pancreatic secretory trypsin inhibitor (hPSTI) mutant that binds to Legionella pneumophila. To gain further insight into the binding kinetics of the isolated hPSTI mutant, an immunosensing system based on a quartz crystal microbalance (QCM) was used. In contrast to ELISA procedures, k(on) and k(off) rates could be derived from the QCM sensograms. Thus, it is possible to characterize specific intermolecular interactions between proteins and phages isolated from large phage display libraries by QCM.

Determination of phage antibody affinities to antigen by a microbalance sensor system

Over the past decade, phage display has maturated to be a frequently used method for the generation of monoclonal antibodies of human origin. The essential step of this method is the "biopanning" of phage carrying functional antibody fragments on their surface on an immobilized antigen. The screening of large combinatorial gene libraries with this method usually leads to a set of diverse clones specifically binding to the antigen that need to be characterized further. Beside its specificity, the key parameter to be determined is the affinity of the recombinant antibody fragment to its antigen. Here, we present a mass sensitive microsensor method that allows the estimation of antibody affinity directly from the phage supernatant. Binding of phage antibodies to the antigen immobilized on a quartz crystal microbalance (QCM) induced a mass dependent decrease in frequency. This principle was used to determine the apparent affinity of a single-chain (sc)Fv antibody against the RNA polymerase of Drosophila melanogaster presented on the surface of a filamentous phage (M13) from its association and dissociation rates. The apparent affinity obtained is in accordance with the affinity of the scFv fragment as determined by conventional equilibrium enzyme-linked immunosorbent assay (ELISA) and plasmon resonance methods.

Quartz crystal microbalance (QCM) as a device for the screening of phage libraries

An immunosensing system based on a quartz crystal microbalance (QCM) is presented for the selection of both antigen specific recombinant antibodies and antigen specific human pancreatic secretory trypsin inhibitor (hPSTI) mutants isolated from large phage libraries. The QCM was integrated into a flow injection analysis system for the straightforward analysis of large sample numbers. Measurements were performed using a biotinylated antigen immobilized by streptavidin onto the gold surface of the quartz crystal and phages displaying recombinant antibodies or hPSTI mutants. The results obtained by the QCM were in accordance to those of a well established enzyme linked immunosorbent assay (ELISA). Therefore, the QCM is well suited for the detection of single high affinity clones isolated from large phage display libraries.

7 alpha-Biotinylated testosterone derivatives as tracers for a competitive chemiluminescence immunoassay of testosterone in serum

Ring core-biotinylated testosterone tracers were synthesized with bridges of three different lengths connecting the biotin moiety to the steroid core (7 alpha-Cn-Bio-T, n = 3, 6, or 11). Together with a position 7-specific polyclonal anti-testosterone antibody, we used the 7 alpha-C11-Bio-T tracer to develop a novel, labeled-hapten competitive immunoassay for total testosterone in serum. (The C3 and C6 tracers proved to be not suitable for analogous immunoassays.) Enhanced chemiluminescence signal was generated by use of a second immobilized antibody and a streptavidin-horseradish peroxidase conjugate. The measuring range of the assay is 0.2-20.0 nmol/L, linearity of serial dilutions can be demonstrated, the lower detection limit is 0.125 nmol/L, and the interassay imprecisions are 13-16%. Accuracy determinations in mass spectrometry-controlled reference specimens showed a mean recovery of 95%. In addition, the assay shows low cross-reactivities, demonstrating the favorable specificity of the combination of a "nearly native" tracer with a position analog antibody. The optimized steric structure and the long spacer arm of the biotinylated testosterone tracer make this chemiluminescence assay well-suited for measuring total testosterone concentration in serum.

Sixty-minute alteplase protocol: a new accelerated recombinant tissue-type plasminogen activator regimen for thrombolysis in acute myocardial infarction

OBJECTIVES

Our aim was to design and evaluate a new and easily administered recombinant tissue-type plasminogen activator (rt-PA) regimen for thrombolysis in acute myocardial infarction (AMI) based on established pharmacokinetic data that improve the reperfusion success rate.

BACKGROUND

Rapid restoration of Thrombolysis in Myocardial Infarction (TIMI) grade 3 flow is a primary predictor of mortality after thrombolysis in AMI. However, TIMI grade 3 patency rates 90 min into thrombolysis of only 50% to 60% indicate an obvious need for improved thrombolytic regimens.

METHODS

Pharmacokinetic simulations were performed to design a new rt-PA regimen. We aimed for a plateau tissue-type plasminogen activator (t-PA) plasma level similar to that of the first plateau of the Neuhaus regimen. These aims were achieved with a 20-mg rt-PA intravenous (i.v.) bolus followed by an 80-mg i.v. infusion over 60 min (regimen A). This regimen was tested in a consecutive comparative trial in 80 patients versus 2.25 10(6) IU of streptokinase/60 min (B), and 70 mg (C) or 100 mg (D) of rt-PA over 90 min. Subsequently, a confirmation trial of regimen A in 254 consecutive patients was performed with angiographic assessment by independent investigators of patency at 90 min.

RESULTS

The comparative phase of the trial yielded, respectively, TIMI grade 3 and total patency (TIMI grades 2 and 3) of 80% and 85% (regimen A), 35% and 50% (B), 50% and 55% (C) and 60% and 70% (D). In the confirmation phase of the trial, regimen A yielded 81.1% TIMI grade 3 and 87.0% total patency. At follow-up angiography 7 (4.1%) of 169 vessels had reoccluded. In-hospital mortality rate was 1.2%. Nadir levels of fibrinogen, plasminogen and alpha2-antiplasmin were 3.6 +/- 0.8 mg/ml, 60 +/- 21% and 42 +/- 16%, respectively (mean +/- SD). Fifty-seven patients (22.4%) suffered from bleeding; 3.5% needed blood transfusions.

CONCLUSIONS

The 60-min alteplase thrombolysis in AMI protocol achieved a TIMI grade 3 patency rate of 81.1% at 90 min with no indication of an increased bleeding hazard; it was associated with a 1.2% overall mortality rate. These results are substantially better than those reported from all currently utilized regimens. Head to head comparison with established thrombolytic regimens in a large-scale randomized trial is warranted.

Synthesis of 17 beta-hydroxyandrost-4-en-3-one-7 alpha-(biotinyl-6-N-hexylamide), a conjugate useful for affinity chromatography and for testosterone immunoassays

We describe the synthesis of 17 beta-hydroxyandrost-4-en-3-one-7 alpha-(biotinyl-6-N-hexylamide) from 17 beta-hydroxyandrost-4-en-3-one (testosterone) via copper-catalyzed 1,6 Michael addition of a 6-(tertbutyldimethylsilyloxyhexyl) chain to 6-dehydrotestosterone 17 beta-acetate. After chromatographic separation of the 7 alpha-isomer from the alpha / beta mixture and cleavage of the silyl ether, the alcohol was oxidized to the 6-hexanal side chain and then subjected to reductive amination. The resulting primary amine is easily biotinylated using biotinyl-N-hydroxysuccinimide ester. The overall yield for the epimeric 7 alpha-end product was 30%. The absolute configurations of the epimers were investigated by 1H NMR studies by the nuclear Overhauser effect. We introduced a biotin label to the testosterone molecule at ring position 7 in compliance with Landsteiner's principle, which states that antibody specificity is directed primarily at that portion of the hapten furthest from the functional group linking it to the carrier protein. Thus, this negligible alteration in comparison to the structure of the respective testosterone hapten used to elicit antibodies offers the feasibility of applying the testosterone derivative as an optimal immunoadsorbent in affinity chromatography. The 7 alpha-biotinylated testosterone was used to obtain active antitestosterone antibodies from a specific antiserum by affinity chromatography. This was achieved by attaching the biotinylated testosterone to agarose-coupled streptavidin beads. Accordingly, a 3H-testosterone-binding test demonstrated a 20-fold increase in affinity of the purified antibody to the steroid compared to the original antiserum, and a recovery of > 80% could be obtained. The antitestosterone antibody, obtained by that method, is an effective component for use in a competitive immunoassay for testosterone in human sera. An assay configuration is conceivable with the same 7 alpha-biotinylated testosterone employed as tracer in combination with a streptavidin-linked reporter enzyme.

6 alpha-biotinylated estrone: novel tracer in competitive chemiluminescence immunoassay of estrone in serum

We describe the development and validation of a labeled-hapten competitive immunoassay for determining total estrone in serum. For the hapten tracer we use the 6 alpha-biotinylated estrone derivative, 3-hydroxyestra-1,3,5(10)-trien-17-one 6 alpha-N-(epsilon-biotinyl)aminocaproamide (Bio-E1). A specific polyclonal rabbit anti-estrone antibody is indirectly bound via an immobilized donkey anti-rabbit antibody on microtiter plate wells. The amount of Bio-E1 bound is then measured with streptavidin-horseradish peroxidase conjugate, whereby the enzyme activity is quantified by an enhanced chemiluminometric method. For the assay, serum samples were extracted with solid-phase extraction cartridges. The assay dynamic range was 93-7400 pmol/L estrone, with a lower detection limit of 55 pmol/L. An interassay imprecision (CV) of 12-14%, a recovery rate between 80% and 110%, and a dilution linearity are demonstrated. Estrone serum concentrations were measured in healthy men and women and in women with polycystic ovary syndrome. Comparing the assay with a nonextraction RIA, we found an acceptable correlation for samples from 143 subjects of either sex. This enzyme immunoassay with biotin as the primary label and enhanced chemiluminescence signaling detection performs well for determining total estrone in serum and is readily adaptable to assays for other steroid hormones.

6 alpha-biotinylated estrone: novel tracer in competitive chemiluminescence immunoassay of estrone in serum

We describe the development and validation of a labeled-hapten competitive immunoassay for determining total estrone in serum. For the hapten tracer we use the 6 alpha-biotinylated estrone derivative, 3-hydroxyestra-1,3,5(10)-trien-17-one 6 alpha-N-(epsilon-biotinyl)aminocaproamide (Bio-E1). A specific polyclonal rabbit anti-estrone antibody is indirectly bound via an immobilized donkey anti-rabbit antibody on microtiter plate wells. The amount of Bio-E1 bound is then measured with streptavidin-horseradish peroxidase conjugate, whereby the enzyme activity is quantified by an enhanced chemiluminometric method. For the assay, serum samples were extracted with solid-phase extraction cartridges. The assay dynamic range was 93-7400 pmol/L estrone, with a lower detection limit of 55 pmol/L. An interassay imprecision (CV) of 12-14%, a recovery rate between 80% and 110%, and a dilution linearity are demonstrated. Estrone serum concentrations were measured in healthy men and women and in women with polycystic ovary syndrome. Comparing the assay with a nonextraction RIA, we found an acceptable correlation for samples from 143 subjects of either sex. This enzyme immunoassay with biotin as the primary label and enhanced chemiluminescence signaling detection performs well for determining total estrone in serum and is readily adaptable to assays for other steroid hormones.

Vectorcardiographic monitoring to assess early vessel patency after reperfusion therapy for acute myocardial infarction

Reperfusion therapy has lowered mortality in patients suffering from acute myocardial infarction. Failure to reperfuse is associated with an increased short- and long-term mortality. In a prospective study we used dynamic vectorcardiography to monitor 96 patients with acute myocardial infarction treated with reperfusion therapy to non-invasively assess coronary patency. The results from continuous monitoring were compared to those obtained from angiography. By using trend-analysis of QRS vector difference and ST vector magnitude, we were able to correctly identify 58 of the 70 patients (83%) with a reperfused infarct-related artery, and 19 of the 26 patients (73%) with a persistently occluded artery demonstrated at an early angiogram (diagnostic accuracy 80%). In patients with high-grade collateral flow to the infarct-related area, the results of the vectorcardiographic monitoring and of angiography showed the largest disagreement, whereas the accuracy of vectorcardiographic monitoring was high: 88% among patients without collaterals. The present results suggest that QRS complex and ST segment vectorcardiographic monitoring is a useful tool for assessing early coronary artery patency, and that dynamic vectorcardiography may help in identifying candidates for emergency coronary angiography.

Respiratory chain and mitochondrial deoxyribonucleic acid in blood cells from patients with focal and generalized dystonia

An increasing number of neurodegenerative diseases seem to be associated with or even due to disturbances of cerebral energy metabolism. One generally accepted example is complex I deficiency in substantia nigra from patients with Parkinson's disease. Reports on a complex I defect in platelets from patients with dystonia led us to check for disturbances of the respiratory chain or of the mitochondrial genome in isolated mitochondria from patients with focal or generalized dystonia. We could not confirm the idea of mitochondrial disturbance in platelets from patients with dystonia because we did not find abnormal enzyme activities or any deletions of the mitochondrial genome. Thus, we do not think that blood cells such as platelets can serve as markers for neurodegenerative disorders such as dystonia.

Unaltered aconitase activity, but decreased complex I activity in substantia nigra pars compacta of patients with Parkinson's disease

Substantia nigra pars compacta of seven patients who had died of Parkinson's disease, has been investigated for the iron-depending aconitase (reactions I and II). In addition we analysed respiratory chain enzymes. While complex I activity of the respiratory chain was significantly reduced, other enzymes of this pathway were unaltered. The citric acid cycle enzyme aconitase (reactions I and II) showed no difference between patients and controls. Thus this ferrous iron dependent and oxidatively sensitive enzyme is not affected by the unphysiological high amount of ferric iron and the 'oxidative stress' present in substantia nigra of parkinsonian patients.