Novel Human Acute Ischemic Stroke Blood Clot Analogs for In Vitro Thrombectomy Testing

BACKGROUND AND PURPOSE

Previous studies have successfully created blood clot analogs for in vitro endovascular device testing using animal blood of various species. Blood components vary greatly among species; therefore, creating clot analogs from human blood is likely a more accurate representation of thrombi formed in the human vasculature.

MATERIALS AND METHODS

Following approval from the Mayo Clinic institutional review board, human whole-blood and platelet donations were obtained from the blood transfusion service. Twelve clot analogs were created by combining different ratios of red blood cells + buffy coat, plasma, and platelets. Thrombin and calcium chloride were added to stimulate coagulation. Clot composition was assessed using histologic and immunohistochemical staining. To assess the similarities of mechanical properties to patient clots, 3 types of clot analogs (soft, elastic, and stiff) were selected for in vitro thrombectomy testing.

RESULTS

The range of histopathologic compositions produced is representative of clots removed during thrombectomy procedures. The red blood cell composition ranged from 8.9% to 91.4%, and fibrin composition ranged from 3.1% to 53.4%. Platelets (CD42b) and von Willebrand Factor ranged from 0.5% to 47.1% and 1.0% to 63.4%, respectively. The soft clots had the highest first-pass effect and successful revascularization rates followed by the elastic and stiff clots. Distal embolization events were observed when clot ingestion could not be achieved, requiring device pullback. The incidence rate of distal embolization was the highest for the stiff clots due to the weak clot/device integration.

CONCLUSIONS

Red blood cell-rich, fibrin-rich, and platelet-rich clot analogs that mimic clots retrieved from patients with acute ischemic stroke were created in vitro. Differing retrieval outcomes were confirmed using in vitro thrombectomy testing in a subset of clots.

The Relationship Between Cerebral Reperfusion And Regional Expression Of Matrix Metalloproteinase-9 In Rat Brain Following Focal Cerebral Ischemia

We investigated the effect of full and partial mechanical reperfusion on MMP-9 expression in rat brain following middle cerebral artery occlusion, mimicking mechanical thrombectomy. Using percentage hemispheric lesion volume and oedema as measures, partial reperfusion reduced extent of brain damage caused by MCA occlusion, but the protective effect was less pronounced than with complete reperfusion. Using ELISA quantification in fresh frozen tissue, confirmed by immunofluorescence in perfusion fixed tissue, increased MMP-9 expression was observed in infarcted tissue. MMP-9 was increased in lesioned tissue of the anterior and posterior temporal cortex and underlying striatal tissue, but also the normal appearing frontal cortex. No significant increase in MMP-9 in the hippocampus was observed, nor in the unlesioned contralateral hemisphere. Both partial reperfusion and full reperfusion reduced the regional MMP expression significantly. The highest levels of MMP-9 were observed in lesioned brain regions in the non-reperfused group. MMP-9 expression was evident in microvessels and in neuronal cell bodies of affected tissue. This study shows that MMP-9 brain levels are reduced relative to the extent of reperfusion. These observations suggest targeting early increases in MMP-9 expression as a possible neuroprotective therapeutic strategy and highlight the rat MCA occlusion model as an ideal model in which to study candidate therapeutics.

Animal Models of Focal Cerebral Ischaemia and Haemorrhagic Transformation: Considerations in Experimental Stroke Study Design

BACKGROUND

Ischaemic stroke is often complicated with haemorrhage within the infarct zone or in a remote location especially when treated with intravenous thrombolysis and/or thrombectomy. While these early recanalisation treatments are highly effective, some of the benefit is lost because of haemorrhagic complications and consequential neurological deterioration of the patients. A number of mechanisms have been described that mediate the haemorrhagic changes and several agents have been tested in experimental models for inhibiting post-stroke haemorrhage.

METHODS

Here, we review and discuss the small animal models of focal cerebral ischaemia and postischaemic stroke haemorrhagic transformation and how these models can best be utilised for developing further insights as well as potential treatment approaches for this serious clinical complication.

RESULTS

The need to use appropriate animal models with relevant stroke risk factors to improve the clinical relevance and applicability of findings is becoming ever more apparent. Current focal ischaemia models can be adapted for the study of haemorrhagic transformation post-stroke.

CONCLUSION

A number of factors can be added to the animal model design to increase the incidence and/or severity of haemorrhagic transformation post-ischaemic stroke, which can improve clinical relevance, aid the study of the pathophysiology and the future development of novel interventions.

The actuation of a biomimetic poly(vinyl alcohol)poly(acrylic acid) gel

Active polymer gels expand and contract in response to certain environmental stimuli, such as the application of an electric field or a change in the pH level of the surroundings. This ability to achieve large, reversible deformations with no external mechanical loading has generated much interest in the use of these gels as biomimetic actuators and "artificial muscles". In previous work, a thermodynamically consistent finite-elastic constitutive model has been developed to describe the mechanical and actuation behaviours of active polymer gels. The mechanical properties were characterized by a free-energy function, and the model uses an evolving internal variable to describe the actuation state. In this work, an evolution law for the internal variable is determined from free actuation experiments on a poly(vinyl alcohol)poly(acrylic acid) (PVAPAA) gel. The complete finite-elastic/evolution law constitutive model is then used to predict the response of the PVA-PAA gel to isotonic and isometric loading and actuation. The model is shown to give relatively good agreement with experimental results.

Modeling tongue surface contours from Cine-MRI images

This study demonstrated that a simple mechanical model of global tongue movement in parallel sagittal planes could be used to quantify tongue motion during speech. The goal was to represent simply the differences in 2D tongue surface shapes and positions during speech movements and in subphonemic speech events such as coarticulation and left-to-right asymmetries. The study used tagged Magnetic Resonance Images to capture motion of the tongue during speech. Measurements were made in three sagittal planes (left, midline, right) during movement from consonants (/k/, /s/) to vowels (/i/, /a/, /u/). MR image-sequences were collected during the C-to-V movement. The image-sequence had seven time-phases (frames), each 56 ms in duration. A global model was used to represent the surface motion. The motions were decomposed into translation, rotation, homogeneous stretch, and in-plane shear. The largest C-to-V shape deformation was from /k/ to /a/. It was composed primarily of vertical compression, horizontal expansion, and downward translation. Coarticulatory effects included a trade-off in which tongue shape accommodation was used to reduce the distance traveled between the C and V. Left-to-right motion asymmetries may have increased rate of motion by reducing the amount of mass to be moved.

Modeling the motion of the internal tongue from tagged cine-MRI images

A new technique, tagged Cine-Magnetic Resonance Imaging (tMRI), was used to develop a mechanical model that represented local, homogeneous, internal tongue deformation during speech. The goal was to infer muscle activity within the tongue from tissue deformations seen on tMRI. Measurements were made in three sagittal slices (left, middle, right) during production of the syllable /ka/. Each slice was superimposed with a grid of tag lines, and the approximately 40 tag line intersections were tracked at 7 time-phases during the syllable. A local model, similar to a finite element analysis, represented planar stretch and shear between the consonant and vowel at 110 probed locations within the tongue. Principal strains were calculated at these locations and revealed internal compression and extension patterns from which inferences could be drawn about the activities of the Verticalis, Hyoglossus, and Superior Longitudinal muscles, among others.

Changing incidence of Achilles tendon rupture in Scotland: a 15-year study

OBJECTIVE

To determine the incidence of Achilles tendon rupture in Scotland from 1980 to 1995.

DESIGN

Retrospective analysis of prospectively collected data.

SETTING

Data were obtained from the National Health Service Information and Statistics Division and analyzed in terms of age- and gender-specific incidence rates and time trends by age group.

PARTICIPANTS

A total of 4,201 patients with Achilles tendon ruptures occurring during the study period.

MAIN OUTCOME MEASURES

Calculation of incidence and of seasonality.

RESULTS

The overall incidence of Achilles tendon rupture increased from 4.7/100,000 in 1981 to 6/100,000 in 1994, with a peak in 1986. In men, the incidence rose from 6.3/100,000 to 7.3/100,000. In women, the increase in incidence was more pronounced, from 3/100,000 to 4.7/100,000. In men, peak incidence rate occurred in the 30- to 39-year age group, whereas in women, the peak age-specific incidence occurred in those aged 80 years and older, with a steady increase after age 60. There was no evidence of a seasonality effect in the rate of occurrence of Achilles tendon rupture. A bimodal distribution of age at time of Achilles tendon rupture was noted.

CONCLUSION

There was a significant increase in the incidence of Achilles tendon rupture during the period from 1980 to 1995. This reflects the increased incidence of the injury noted in other Northern European countries.

Seasonality, but not prevalence of sudden infant death syndrome varies by region in mainland Britain

This study aimed to investigate whether seasonal variation in day length contributed to winter/summer variation in sudden infant death syndrome (SIDS) at different latitudes in mainland Britain. Over 11 yrs 13,973 deaths were studied. Using appropriate analytic techniques a sine curve was fitted to monthly rates with the amplitude indicating magnitude of seasonal change. The rate of SIDS per 1,000 live births was the same (1.73) in the north as in the south. The amplitude was a quarter less in the north (41.3%) than in the south (54.2%) (p<0.001). While annual rates did not differ, the within year distribution did. The findings for seasonality of SIDS births were similar (amplitudes: north 213%, south 32.3%). Correlations were made between SIDS amplitude and individual environmental factors, particularly temperature and day length. These complex issues, while reported briefly, do not allow firm conclusions. In the north the winter day length is shorter, sunshine hours are less and temperature is lower, but the winter increment in SIDS is less. The extent of seasonal variation of sudden infant death syndrome is greater in the south as compared with the colder, darker north but this has no effect on sudden infant death syndrome rates. Changing photoperiod by latitude, amongst other environmental influences, may hold clues to the aetiology of sudden infant death syndrome.

Does vitamin D deficiency account for ethnic differences in tuberculosis seasonality in the UK?

OBJECTIVES

Notifications of tuberculosis in England and Wales are reported to peak in the summer season. The purpose of this study was to confirm that finding and to determine to what extent patients of Indian Subcontinent (ISC) ethnic origin contributed to the seasonality. The clinical presentation of the disease is presumed to occur some months following reactivation of the endogenous latent focus of tuberculosis infection. There arises the possibility of vitamin D deficiency producing immunological inadequacy at the end of winter and beginning of spring.

PATIENTS AND METHODS

Monthly (or 4-weekly) aggregated data over 7 years were collected from the three countries of mainland Britain, England, Wales, Scotland and from the city of Birmingham in England. The notifications from Birmingham were divided into those of ISC ethnic origin and 'whites'. The presence or absence of seasonality was determined by fitting a sinusoidal curve by the technique called 'cosinor analysis'. In this method amplitude gives a measure of the extent of the seasonal variation.

RESULTS

The summer peak of clinical diagnosis was confirmed in the UK series from England, Wales and Scotland. In England and Wales without Scotland a larger seasonal variation was present. Scotland, with a lower proportion of population of ISC ethnic origin, was examined separately and the results in Scotland alone failed to confirm seasonality. In the data from Birmingham, seasonality was confirmed with a greater amplitude, particularly in those over 60 years of age. The finding was influenced by those of ISC ethnic origin, seasonality not being present in the 'white' population.

CONCLUSION

The results from Birmingham are very striking, but there were almost three times as many patients in the ISC ethnic group as in indigenous 'white' patients. A series with larger numbers of 'white' patients would be necessary to confirm the absence of seasonality in the 'white' population. The discussion reviews the evidence that vitamin D may have an important hormonal role in immunological defence in the prevention of tuberculosis.

Seasonality of sudden infant death syndrome (SIDS) by age at death

Seasonality of sudden infant death syndrome (SIDS) is a well-established epidemiological finding. The purpose of the study was to determine whether this feature varied significantly with age at death. In total, 13990 cases of SIDS in Scotland, England and Wales during 1982-1992 were studied by age group at death. Seasonality was established by fitting a sinusoidal curve and for each set of monthly data the peak position in the year and its magnitude were determined. Weighted regression revealed significant differences in peak position and amplitude of seasonal variation between those dying at < or = 4 months and those aged > or = 5 months at death. Those infants in the younger age group were more likely to die earlier in the winter months and had a smaller variation in seasonality. The peak (acrophase) months were January for < or = 4 months and February for > or = 5 months at death. Weighted regressions of peak position and amplitude on age at death had p-values of <0.001 and <0.01, respectively. A log linear model relating SIDS incidence to month of birth, month of death and age was able to explain some of these findings. The findings support the hypothesis that in SIDS there may be more than one infant cohort, each of which passes through a vulnerable developmental window at different ages.

Seasonality of sudden infant death syndrome in mainland Britain and Ireland 1985-95

By the end of 1995 four years had passed since the dramatic fall in the incidence of sudden infant death syndrome (SIDS), following the "back to sleep" campaign. This time lag permitted a more definitive epidemiological reassessment than had been possible before. The extent of seasonal variation from 1992-5 fell by about half, occurring mainly as a single step down in 1992. The fall was relatively greater in winter than in summer. Before 1992 the extent of seasonal variation (amplitude) was greater in those age > or = 5 months compared with those aged < or = 4 months. Since 1992 the falls in incidence and amplitude have been greater in the younger group, suggesting that SIDS deaths in younger and older babies may have different causes.

Seasonality and other epidemiological features of haemolytic uraemic syndrome and E. coli O157 isolates in Scotland

The main objective was to determine whether there was seasonality in presentation of haemolytic uraemic syndrome (HUS) in children and adults, and compare this with the reporting of E. coli O157. The data came from Scotland, examining admissions during 1980-95 and E. coli isolates 1984-95. Seasonality was sought by fitting a sine curve to monthly or four-weekly data throughout the year. Seasonality was present for HUS and E. coli isolates in patients under 15 years of age but not in those above that age. The highest point of the sine curve was in July/August but there was a high plateau from June to September. The timing was similar to other diarrhoeal disease. This is an epidemiological study, the purpose being to clarify the seasonal features of HUS. E. coli infection is an important food hazard and a sound knowledge of the epidemiology, could lead to optimal control. The Scottish geographic distribution is illustrated.

Seasonal changes in psychological well-being in an elderly population

BACKGROUND

Little is known about seasonal fluctuations in psychological well-being among elderly people.

METHOD

Over a period of 21 months, 1466 elderly people completed the General Health Questionnaire and the Leeds Scales for Depression and Anxiety. Scores during the winter months (December to February) were compared with those during other months of the year.

RESULTS

Scores on all scales were significantly higher during the winter months, but there was no difference in rates of caseness. Unlike younger populations, elderly women did not exhibit greater seasonality in well-being than did elderly men.

CONCLUSIONS

Elderly people exhibit a small seasonal fluctuation in psychological well-being, which is probably of little clinical importance, and there is no gender difference. The findings support the contention that seasonal mood changes are most pronounced among females of reproductive age.

Circannual rhythm of measles subsequent to immunisation

This is an epidemiological study of biennial and annual rhythms of measles in England and Wales between 1959-1994 highlighting changes following immunisation. The study describes annual rhythms starting in autumn (Week 41) and the statistical method tests the fit of a sine curve to annual data. Before immunisation the previously established biennial rhythm was seen: the two years differed in magnitude of seasonal variation, position of the peak, "visibility of school holidays" and peak breadth. After immunisation (1968) these biennial features tended to disappear, one annual rhythm becoming the predominant feature. By the late eighties adjacent years had very similar sine curve fits. About 1990 (89-91) the fit of the sine curve was no longer significant, was of low amplitude and numbers were at an all time low. In 1992 significant annual variation returned, numbers rose and magnitude of seasonal variation increased. At this time a new epidemic was being predicted on other evidence and this renewed sine curve fit may be an additional warning signal. A possible influence of normal birth rhythm on numbers of susceptibles is described.

Month of birth as an independent variable in the sudden infant death syndrome

Well-known epidemiological features of sudden infant death syndrome (SIDS) are age at death and the increased numbers in winter. There are more SIDS deaths in late autumn/early winter and there is a seasonal rhythm of births with a peak in late summer and early autumn. The data set was 14033 SIDS deaths from Scotland, England and Wales over the 11 years 1982-92. Using log-linear models, which accounted for age at death and month of death, birth month was found to be a statistically significant risk factor for SIDS independent of age at death and winter environment (P < 0.001). Although winter season had the largest effect (relative risk 2.7 in January compared with August), the independent effect of birth month was of clinical as well as statistical significance with a relative risk for August births of 1.37 compared with those born in April. The analysis of each birth month cohort revealed a change in age distribution with infants born in early winter (December) dying at a younger age (mean 108 days) than those born in midsummer (June) (mean 146 days). Although winter season and age are the most influential factors, the substantial effect of month of birth requires explanation and points to as yet unidentified environmental influences during pregnancy.

Infectious mononucleosis and Hodgkin's disease--a similar seasonality

The presentation of Hodgkin's disease and acute infectious mononucleosis (glandular fever) due to Epstein-Barr virus, have similar seasonal features with the peak incidence around March. The extent of seasonal variation is also similar. Seasonality of Hodgkin's disease is most obvious and also significant in adult age groups below the age of 40. Amongst those over 40 years, seasonality was no longer present in the 40-59 but returned over age 60. Seasonal similarity does not prove a relationship. However two speculations are made on possible mechanisms. Firstly glandular fever may accelerate presentation in young adults, destined to present with HD. Secondly the Epstein-Barr virus may have an inherent seasonal behaviour whether causing acute infectious mononucleosis or when latent and playing a role in the aetiology of Hodgkin's disease.

Seasonality of tuberculosis: the reverse of other respiratory diseases in the UK

BACKGROUND

In Western societies there is a winter peak in mortality, largely accounted for by respiratory and cardiovascular deaths. In view of the known seasonal variation in vitamin D, and of the postulated link between tuberculosis and vitamin D deficiency, a study was undertaken to examine whether the presentation of tuberculosis had the same seasonal rhythm as other pulmonary infections.

METHODS

Using cosinor analysis the presence or absence of seasonality was determined for 57,313 tuberculosis notifications for England and Wales. OPCS data in four weekly notifications over a 10 year period (1983-92) were examined as two quinquential sets (1983-7 and 1988-92). These were compared with two groups of acute respiratory illness: 138,992 notifications to OPCS of pneumonia deaths for 1988-92 and all admissions to Scottish hospitals with respiratory disease (252,163 cases) during 1980-4.

RESULTS

Analysis of notifications of tuberculosis revealed a summer peak with an amplitude of 10%. This pattern differs markedly from other respiratory disorders in which a winter peak and summer trough is observed.

CONCLUSIONS

The unusual seasonality of tuberculosis is currently unexplained. One possibility is that low post-winter trough levels of vitamin D (which are known to affect macrophage function and cell mediated immunity) might result in impaired cellular immunity leading, after a latent period, to reactivation of dormant mycobacterial infection.

Seasonal variation in sudden infant death syndrome and bronchiolitis--a common mechanism?

The purpose of this study was to compare epidemiologic features of sudden infant death syndrome (SIDS) and bronchiolitis and to apply statistical examination in order to examine the hypothesis that similar mechanisms could be at work in both conditions. The setting was Scotland from 1982 through 1990. We compared 1,211 deaths from SIDS with 10,058 hospital admissions for bronchiolitis in infancy. The comparisons included age, sex ratio, and seasonality. The sex ratios were similar (SIDS [M:F]:1.61:1; bronchiolitis: 1.63:1), but age distribution was different (chi 2 = 104.6, p < 0.001). When monthly rates throughout the year were compared using correlation of residuals from average season variation and by autocorrelation of residual series, no significant relationships were found between the two conditions (r2 = 0.0004). Once the seasonal pattern common to both conditions was accounted for, SIDS was not autocorrelated between months whereas bronchiolitis exhibited a high level of autocorrelation indicating an epidemic pattern for the latter but not for the former. While a common seasonal variation may indicate some shared etiologic factors associated with winter season, the two conditions do not appear to be closely related. The hypothesis that a common host susceptibility is at work is not supported. Further investigations of seasonal influences are warranted.

Seasonality and the sudden infant death syndrome during 1987-9 and 1991-3 in Australia and Britain

OBJECTIVE

To determine whether seasonality of the sudden infant death syndrome persists now that rates have fallen, mostly after widespread adoption of the "face upwards" sleeping position.

DESIGN

Monthly data on the sudden infant death syndrome during 1987-9 were compared for seasonality with those of 1991-3; rates were studied as deaths per 1000 live births.

SETTING

Australia and Britain (England, Wales, and Scotland).

SUBJECTS

Infants under 1 year dying of the syndrome (2401 for Australia and 6630 for Britain).

MAIN OUTCOME MEASURE

Extent of seasonal variation (amplitude) was established by cosinor analysis; amplitudes for the earlier and later years were compared.

RESULTS

The rate fell in every month, and, though it did so relatively more in winter than summer, seasonality remained a distinctive feature. In the comparison of amplitudes the ratio between the earlier and later years was 1.4 in both Australia and Britain. Some differences between the hemispheres were noted.

CONCLUSIONS

Seasonality of the sudden infant death syndrome remains to be explained and continues to be an important aetiological lead. Studies from other countries are needed.

Seasonal differences in biochemical parameters of bone remodelling

AIMS

To compare bone remodelling parameters in late autumn and early spring in 20 post-menopausal women.

METHODS

The parameters measured were serum osteocalcin and its apparent degree of carboxylation (measured by hydroxyapatite binding), total and bone specific alkaline phosphatase and urinary bone resorption markers, (pyridinoline and deoxypyridinoline).

RESULTS

Serum osteocalcin concentrations were lower in autumn than in spring but the degree of carboxylation was similar. Total and bone specific alkaline phosphatase activities in serum were higher in autumn than in spring. These results support previous observations. However, notable and previously unreported changes in urinary bone resorption markers were observed. Pyridinoline concentrations were lower and deoxypyridinoline higher in autumn compared with spring. The ratio of pyridinoline:deoxypyridinoline was therefore very different between the seasons.

CONCLUSIONS

The results clearly demonstrate that seasonal changes in these variables of bone remodelling must be taken into consideration when designing, reporting or analysing studies of bone metabolism in vivo.

Seasonality of birth in sudden infant death syndrome

The objective was to clarify the optimal birth month for avoidance of SIDS and the seasonal characteristic of each birth-month cohort. The statistical method was cosinor analysis, and this established seasonality of SIDS death and births, the extent of this seasonality (amplitude) and the position of the peak (acrophase). There is a lowering of risk, by one third, amongst babies born in February-May compared to those born in August-November. The seasonal variation of death was twice as great for birth in September as compared with those in April. Those born in May-June lived on average six weeks longer than those born in November-April. Advice on subsequent pregnancy delivery date should be given to families who have already experienced SIDS. For those born in autumn there may be two components-the first a genetic or intrauterine component independent of month of birth, and the second an independent effect of interaction with winter environment.

Seasonal variation in coronary heart disease in Scotland

STUDY OBJECTIVE

Seasonality of coronary heart disease (CHD) was examined to determine whether fatal and non-fatal disease have the same annual rhythm.

DESIGN

Time series analysis was carried out on retrospective data over a 10 year period and analysed by age groups ( < 45 to > 75 years) and gender.

SETTING

Data by month were obtained for the years 1962-71. The Registrar General provided information on deaths and the Research and Intelligence Unit of the Scottish Home and Health Department on hospital admissions.

SUBJECTS

In Scotland, between 1962 and 1971, 123 000 patients were admitted to hospital for CHD, of whom 29 000 died. There were a further 97 000 CHD deaths outside hospital. These two groups were also examined as one (coronary incidence) - that is, all coronary deaths and coronary admissions discharged alive. STATISTICAL ANALYSIS AND MAIN RESULTS: Where there was a single annual peak, the sine curve was analysed by cosinor analysis. When there were two peaks the analysis was by normal approximation to Poisson distribution. In younger men (under 45 years) admitted to hospital there was a dominant spring peak and an autumn trough. A bimodal pattern of spring and winter peaks was evident for hospital admissions in older male age groups: with increasing age the spring peak diminished and the winter peak increased. In contrast, female hospital admissions showed a dominant winter/summer pattern of seasonal variation. In male and female CHD deaths seasonal variation showed a dominant pattern of winter peaks and summer troughs, with the winter peak spreading into spring in the two youngest male age groups. CHD incidence in women showed a winter/summer rhythm, but in men the spring peak was dominant up to the age of 55.

CONCLUSION

The male, age related spring peak in CHD hospital admissions suggests there is an androgenic risk factor for myocardial infarction operating through an unknown effector mechanism. As age advances and reproduction becomes less important, the well defined winter/summer pattern of seasonal variation of CHD is superimposed, and shows a close relationship with the environment, especially temperature, or the autumn and early winter fall in temperature.

Decreased axial and peripheral bone density in patients taking long-term warfarin

Impaired vitamin K metabolism is associated with under-carboxylation of the non-collagenous bone-matrix protein osteocalcin, which is required in its fully carboxylated state for normal bone formation. Post-menopausal women have under-carboxylation of osteocalcin which increases with age and is marked in the elderly. A similarly marked degree of impaired carboxylation occurs during coumarin therapy, and a key question is whether this may lead to accelerated loss of bone mass which is clinically important. We measured axial and peripheral bone mineral density (BMD) in 40 male patients on warfarin and 40 controls individually matched for age, disease and other drug therapy. A consistent trend for reduced BMD at all sites was observed in the warfarin-treated patients. This was particularly marked in the cancellous bone at the distal radius (9% reduction, p = 0.023) and at the cancellous rich lumbar spine site (10.4% reduction, p < 0.004). No significant relationship was observed between warfarin dose, International Normalized Ratio (INR) or duration of therapy and bone density. Because of the biochemical similarity, this study provides a new lead on post-menopausal osteoporosis, and supports the hypothesis that impaired carboxylation of osteocalcin plays a role in the pathogenesis of bone loss in the elderly through deficiency in vitamin K metabolism.

Carboxylation of osteocalcin in post-menopausal osteoporotic women following vitamin K and D supplementation

The effect of vitamin supplements on bone metabolism indices in patients with osteoporosis has received scant attention in the literature. Over a 2-week period, vitamin supplements of K and K+D were given to 20 post-menopausal osteoporotic women with previous Colles fractures. Osteoporosis was confirmed by bone mass measurements that demonstrated that broadband ultrasound attenuation (os calcis) was almost as discriminatory as dual energy X-ray absorptiometry (spine and hip) in Colles fracture patients compared with matched controls. Vitamin K corrected the carboxylation defect in osteocalcin and while less marked 4 weeks later, the improvement was still detectable. The result after K+D was similar. The level of carboxylation became the same as in premenopausal women. Total osteocalcin level (bound) osteocalcin. While there was vitamin K correctable undercarboxylation of osteocalcin, simultaneously there was no evidence of undercarboxylation of prothrombin.

Improvements to immunoassays by use of covalent binding assay plates

The uniformity of Xenobind covalent binding microwell plates was compared with that of passive binding plates by binding streptavidin to the plate surface, reacting the streptavidin with biotinylated alkaline phosphatase, and developing color with phenolphthalein monophosphate. Absorbance of the covalent binding plates at 570 nm was 0.95 A (CV 1.9%) compared with 0.35-0.5 A (CV 6.7-16.9%), for passive plates. No edge effect was observed with Xenobind covalent plates. Use of both plates in a model immunoassay gave a CV of 4% for the covalent binding plate and 12-15% for the passive binding plates. Moreover, the background absorbance (color development when no antigen was present) for the covalent binding plates was < 0.05 A in all cases, whereas that for the passive binding plates ranged up to 0.45 A. The high background on passive plates results from displacement of capture antibody and (or) blocking agent from the plate, thereby providing a place for detector antibody binding.

Improvements to immunoassays by use of covalent binding assay plates

The uniformity of Xenobind covalent binding microwell plates was compared with that of passive binding plates by binding streptavidin to the plate surface, reacting the streptavidin with biotinylated alkaline phosphatase, and developing color with phenolphthalein monophosphate. Absorbance of the covalent binding plates at 570 nm was 0.95 A (CV 1.9%) compared with 0.35-0.5 A (CV 6.7-16.9%), for passive plates. No edge effect was observed with Xenobind covalent plates. Use of both plates in a model immunoassay gave a CV of 4% for the covalent binding plate and 12-15% for the passive binding plates. Moreover, the background absorbance (color development when no antigen was present) for the covalent binding plates was &lt; 0.05 A in all cases, whereas that for the passive binding plates ranged up to 0.45 A. The high background on passive plates results from displacement of capture antibody and (or) blocking agent from the plate, thereby providing a place for detector antibody binding.

Changing seasonality of birth--a possible environmental effect

STUDY OBJECTIVE

Seasonality of birth was examined to determine whether this has changed over the last half century.

DESIGN

Time-series analysis was carried out on retrospective data, both for the full 50 year period and for the five decades within that period. Although the primary objective was to investigate seasonality by fitting an appropriate model and examining changes over the period studied, non-seasonal trends were also examined.

SETTING

Data by month were obtained from the Registrar General on all births in Scotland during the years 1938-87.

SUBJECTS

There was a total of 4,325,000 births in the 50 years examined.

MEASUREMENTS AND MAIN RESULTS

There are two peaks to the seasonality rhythm--one wide, in spring/early summer and one narrow, in October. Cosinor analysis, modified to allow for the second peak, was used to fit a sine curve model. Analysis of variance showed that this was adequate and established the significance of both peaks. The main peak of seasonal excess rose to a maximum in 1948-57, and thereafter declined by two thirds. While the position of the main peak moved forward two months over the 50 years, the October peak remained unchanged until the final decade, when it rose slightly; thus its relative importance increased steadily from 1948 onwards.

CONCLUSIONS

The changing biological rhythm may be related to alterations in the climate and environment or to social differences.

Seasonality of hip fracture and haemorrhagic disease of the newborn

The objective is to examine and compare the seasonalities of fractured neck of femur and haemorrhagic disease of the newborn. The data are from two sources. Admissions for fractured neck of femur in Scotland over five years (1983-87) are examined by age, sex, mortality, operative intervention and source of admission. Data from the United States (1927-36) are examined for infant death rates from suspected haemorrhagic disease of the newborn 3-14 days after birth. The sine curves are examined. The rhythms, while not identical, have similarities. The peaks are in January-February and the troughs in July-August. Amongst hip fractures the peak is one month earlier and the seasonal excess around 20-25 per cent in both conditions. Rickets, haemorrhagic disease of the newborn and fractured neck of femur have comparable seasonal rhythms. Vitamin D regulates the synthesis of the vitamin K dependent bone protein osteocalcin, which is functionally abnormal in postmenopausal women. This may be a significant factor in the seasonal variation of hip fracture.

Macroscopic three-dimensional motion patterns of the left ventricle

The pattern of displacements in the left ventricle (LV) can be described by 13 modes of motion and deformation. Three functional modes of deformation are essential for ejection: a decrease in cavity volume, torsion, and ellipticalization. Four additional modes are used to describe asymmetric deformation. Six modes of rigid body motion describe rotation and translation. In the LV 14-20 radiopaque markers were inserted in the wall of the LV. They were distributed more or less evenly from base to apex and around the circumference. Torsion and volume changes require the definition of a cardiac coordinate system. The point at which ejection focuses is used as the origin, and the torsion axis is used as the z-axis. In the present study the coordinate system was positioned objectively by a least squares fit of the kinematic model to the measured motion of markers. In five dogs in the control state the kinematic parameters were determined as a function of time for all 13 modes. The torsion axis was displaced 4 +/- 2 mm (mean +/- sd) from the center of the cross-section of the LV towards the lateral free wall. The direction of the torsion axis closely coincided with anatomical landmarks at the apex and base. During systole, a unique relation was found between the ratio of cavity volume to wall volume and torsion. This relation was universal to all LVs, the cylinder-symmetric mathematical model of cardiac mechanics inclusive. In diastole the patterns of deformation seem less universal and reproducible.

A method to reconstruct myocardial sarcomere lengths and orientations at transmural sites in beating canine hearts

The ability to measure cyclic changes in myocardial sarcomere lengths and orientations during cardiac ejection and filling would improve our understanding of how the cellular processes of contraction relate to the pumping of the whole heart. Previously, only postmortem sarcomere measurements were possible after arresting the heart in one state and fixing it for histology. By combining such histological measurements with direct observations of the deformation experienced by the same myocardial region while the heart was beating, we have developed a method to reconstruct sarcomere lengths and orientations throughout the cardiac cycle and at several transmural layers. A set of small (1 mm) radiopaque beads was implanted in approximately 1 cm3 of the left ventricular free wall. Using biplane cineradiography, we tracked the motion of these markers through various cardiac cycles. To quantify local myocardial deformation (as revealed by the relative motion of the markers), we calculated the local deformation gradient tensors. As the heart deforms, these describe how any short vectorial line segment alters its length and orientation relative to a reference state. Specifically, by choosing the reference state to be the arrested and fixed heart and by measuring the sarcomere vector in that state, we could then use the deformation gradient tensors to reconstruct the sarcomere vector that would exist in the beating heart. As ventricular chamber volume varied over its normal range of operation, the range of reconstructed sarcomere lengths (approximately 1.7-2.4 microns) was comparable to other histological studies and to measurements of sarcomere length in excised papillary muscles or trabeculae. The pattern of sarcomere length changes was markedly different, however, during ejection vs. filling.

Seasonality of disease in Kuwait

To compare the seasonal variation in total mortality and deaths from cardiovascular, respiratory, and malignant disease, data were collected from North-East Scotland (Grampian region) and Kuwait. Seasonal differences were similar, in both timing and degree, for total mortality and deaths from circulatory disease, but were greater in Kuwait for respiratory disease. Peak mortality was during winter in both areas: in Grampian, when the climate is most uncomfortable, and in Kuwait, when the climate is at its most comfortable. Socioeconomic changes in Kuwait have been accompanied by a rapid fall in the degree of seasonality (deseasonality) for both total and infant mortality. These findings suggest that mortality peaks in winter, not because of a seasonally low temperature, but because of a seasonal fall in mean temperature irrespective of the annual mean temperature.

Composition of seasonality of disease

The composition of the seasonality of total death was ascertained. Vascular disease seasonality constitutes more than half. The remaining seasonality is influenced by respiratory disease. Surprisingly and of possible importance cancer mortality was not seasonal. Deaths from 'all other disease' and from 'injuries' is seasonal. Seasonality increases with age. In coronary and cerebrovascular disease death has a large seasonal fluctuation. On the other hand hospital admissions and survivors have a minor seasonal fluctuation--only cerebrovascular admissions reaching the chosen level of significance with a small seasonal amplitude. For vascular disease the ranking of seasonal fluctuation from greatest to least is--death outside hospital, total death, death inside hospital, admissions, survivors. It is death outside hospital presumably 'sudden' that imposes seasonality on coronary disease in general. For respiratory diseases not only death but hospital admissions and survivors have high amplitude seasonality with a much greater fluctuation than for death in vascular disease.

Unique strain history during ejection in canine left ventricle

Understanding the relationship between structure and function in the heart requires a knowledge of the connection between the local behavior of the myocardium (e.g., shortening) and the pumping action of the left ventricle. We asked the question, how do changes in preload and afterload affect the relationship between local myocardial deformation and ventricular volume? To study this, a set of small radiopaque beads was implanted in approximately 1 cm3 of the isolated canine heart left ventricular free wall. Using biplane cineradiography, we tracked the motion of these markers through various cardiac cycles (controlling pre- and afterload) using the relative motion of six markers to quantify the local three dimensional Lagrangian strain. Two different reference states (used to define the strains) were considered. First, we used the configuration of the heart at end diastole for that particular cardiac cycle to define the individual strains (which gave the local "shortening fraction") and the ejection fraction. Second, we used a single reference state for all cardiac cycles i.e., the end-diastolic state at maximum volume, to define absolute strains (which gave local fractional length) and the volume fraction. The individual strain versus ejection fraction trajectories were dependent on preload and afterload. For any one heart, however, each component of absolute strain was more tightly correlated to volume fraction. Around each linear regression, the individual measurements of absolute strain scattered with standard errors that averaged less than 7% of their range. Thus the canine hearts examined had a preferred kinematic (shape) history during ejection, different from the kinematics of filling and independent or pre-or afterload and of stroke volume.

Seasonal, regional and secular variations of cardiovascular and cerebrovascular mortality in New Zealand

Numbers of deaths from coronary heart disease (CHD) and cerebrovascular disease (CVD) were available for five years (1980-84) in the North and South Islands of New Zealand; estimated death rates were determined, and age correction made. There was a major seasonal variation by month in coronary and cerebrovascular deaths in both sexes and both islands, with a zenith in June/July/August (winter) and a nadir in December/January/February (summer). There was a less obvious, and less complete, linear trend, with declining secular (annual) mortality over the five years. This was more obvious in North Island but not proven in South Island. After standardising for age, coronary mortality rates (but not cerebrovascular mortality rates), were significantly higher in South Island than in North Island. Mortality from both CHD and CVD was significantly higher in males than in females.

A Scottish Hebridean antithrombin III deficient family--twelve years on

The members of this family with ATIII deficiency have been followed for at least 12 years (1976-1989). All those with previous venous thrombo-embolism have been free from recurrence when on warfarin. During the half century 1931-1981, all 11 full term pregnancies in four affected patients were associated with venous thromboembolism; one patient was enigmatic having one full term pregnancy, without thrombotic event; between 1982 and 1989 three pregnancies have been actively managed with no clinical thrombosis. Management involved use of monitored, self administered, subcutaneous heparin before or very soon after conception and throughout pregnancy (warfarin having been stopped), planned delivery under cover of intravenous antithrombin III, reduction of heparin dosage at delivery and reintroduction of warfarin in the puerperium. The recognised hazards of heparin therapy in pregnancy did not occur. The involvement of the arterial system is reviewed. Clinical evidence provides tentative suggestions on (a) possible additional risk of cigarette smoking (b) avoidance of venography (c) avoidance of varicose vein surgery. A probe is now available for the defective antithrombin III gene in this family, but there has been no occasion yet to apply this in antenatal diagnosis.

Inhomogeneous deformation as a source of error in strain measurements derived from implanted markers in the canine left ventricle

This article quantifies the errors inherent in the measurement of myocardial strain in the canine left ventricle when the motion of four radiopaque marker beads is used to determine this strain. These errors are introduced because the strain is strongly inhomogeneous and only an averaged value of this strain can be determined by measuring the displacements of four points with finite separation. In this work, the error in the principal strains has been estimated by modeling the primary deformation components of the left ventricle and comparing the true strains obtained from these models with the strains computed according to the protocol typically used in experimental studies to determine strain from the motion of marker beads. Both a cylindrical and a spherical model of the left ventricle are used. For the cylindrical model, it is found that the traditional tetrahedra used may give errors as high as 20% in the maximum principal strain. A six-marker prism is found to give more consistent results, underestimating the maximum principal strain, which is in the radial direction, by no more than 8% in almost all cases. The spherical model, having double curvature, gives larger errors. In both models, the error in the other two principal strains was usually less than 5%. Furthermore, the principal strain directions were correct to within 6 degrees.

Evidence linking familial thrombosis with a defective antithrombin III gene in two British kindreds

Using DNA probes in a structural study of the antithrombin III gene locus we found no evidence of gene deletion in two British kindreds with inherited antithrombin III deficiency. However, linkage analysis between a common DNA polymorphism and the antithrombin III deficiency trait showed that the defect lies at or close to the antithrombin III structural gene. The lod score for linkage within the larger Scottish kindred was 3.1 (theta = 0). These results are consistent with previously published data suggesting that mutation of the antithrombin III structural gene is the cause of inherited antithrombin III deficiency in some families.

Twenty year follow up of patients in the Medical Research Council trial of anticoagulants in acute myocardial infarction

A 20 year follow up of 1330 patients in the Medical Research Council trial of short term anticoagulant treatment in myocardial infarction showed no long term benefits; but it provided interesting data on the outcome in such patients. Sixteen per cent of the patients were alive 20 years later. The excess mortality rate in trial participants over that expected for England and Wales as a whole declined rapidly after the early months, but some excess persisted throughout the follow up. Three quarters of all the deaths were from coronary heart disease; 70% of these coronary deaths occurred after the patients had left hospital. This finding emphasises the importance of secondary prevention.

Aspirin and other antiplatelet drugs in the prophylaxis of thrombosis

Aspirin is of proven value as an antithrombotic drug. In unstable angina it reduces the risk of death and myocardial infarction by half. After a myocardial infarction it reduces the risk of death by about 10% and of coronary incidence (coronary death or definite myocardial infarction) by about 25%. These effects appear to be additive with those of beta-blocking drugs. Aspirin also reduces the risk of occlusion of aortocoronary saphenous vein grafts by about half. In transient cerebral ischaemia, aspirin may reduce the risk of stroke and death by 50%. In most clinical trials to date the daily dose of aspirin ranges from 325 mg to 1400 mg. Interest in very low doses of aspirin (less than 60 mg daily) is considerable but has yet to be translated into proven clinical benefit. Dipyridamole has not been shown to be effective as an antithrombotic when used alone. Its antiplatelet action ex vivo may be enhanced by combination with aspirin but clinical trials have shown relatively little advantage of the combination over aspirin alone. Sulphinpyrazone has not become established as a first line antithrombotic drug. Epoprostenol is useful in extracorporeal circulations to prevent platelet consumption and possibly in severe inoperable peripheral vascular disease.

An international and interregional comparison of haemostatic variables in the study of ischaemic heart disease. Report of a working group

Levels of haemostatic variables that may be involved in thrombogenesis have been compared in groups of men of similar mean age in communities at very low (Gambia), high (England and Czechoslovakia) or very high (Scotland and Finland) risk of ischaemic heart disease (IHD). There was a consistent gradient of higher factor VII levels with higher IHD risk and also suggestive gradients in the case of two other vitamin K dependent factors, factors II and X. Mean platelet counts were lower and mean fibrinolytic activity was greater in Gambian men than in European men. There was a suggestive though not entirely consistent association between mean fibrinogen levels and IHD risk in the groups from IHD-endemic countries. The results as a whole, and particularly those on factor VII, strengthen the case for the increasingly detailed epidemiological as well as laboratory investigation of the role of the haemostatic system in thrombogenesis and IHD.