Fracture prevention by femoroplasty--cement augmentation of the proximal femur

The prevention of hip fractures is a desirable goal to reduce morbidity, mortality, and socio-economic burden. We evaluated the influence on femoral strength of different clinically applicable cementing techniques as "femoroplasty." Twenty-eight human cadaveric femora were augmented by means of four clinically applicable percutaneous cementing techniques and then tested biomechanically against their native contralateral control to determine fracture strength in an established biomechanical model mimicking a fall on the greater trochanter. The energy applied until fracture could be significantly increased by two of the methods by 160% (53.1 Nm vs. 20.4 Nm, p < 0.001) and 164% (47.1 Nm vs. 17.8 Nm, p = 0.008), respectively. The peak load to failure was significantly increased by three of the methods by 23% (3818.3 N vs. 3095.7 N, p = 0.003), 35% (3698.4 N vs. 2737.5 N, p = 0.007), and 12% (3056.8 N vs. 2742.8 N, p = 0.005), respectively. The femora augmented with cemented double drill holes had a lower fracture strength than the single drilled ones. Experimental femoroplasty is a technically feasible procedure for the prophylactic reinforcement of the osteoporotic proximal femur and, hence, could be an auxiliary treatment option to protect the proximal femur against osteoporotic fractures.

Speech processing in radiology

The goal of this study was to evaluate the recognition rate, learning potential and amount of time needed to complete a report with the Philips speech recognition system SP 6000 (Philips, Best, The Netherlands). Four radiologists dictated reports of interventional radiology, MRI examinations of the musculoskeletal system and CT examinations of the thorax and abdomen with the Philips system using the German language. The recognition rate of each report and improvement rate after each learning phase of the Philips system was assessed. The time needed to complete a report using the Philips system was then compared with the time needed to complete a report using the tape-based system via a time analysis. The average recognition rate for the four radiologists using the Philips system was 79.6 %, which improved to 92.5 % after the third adaptation. Initially, the average time demand to dictate and correct one report was approximately 16.8 min, but this time decreased to 8.1 min after the third adaptation. In contrast, only 3. 6 min were needed to dictate and correct one report using the tape-based system. However, with the speech recognition system, dictation, correction and transcription of the report can be completed within 15 min, whereas with the tape-based system, it takes nearly 1 day. With the Philips system, speech recognition can reach as high as 95 % since each adaptation of the system improves the recognition rate by approximately 5 %. While the Philips system is associated with longer dictation times than the tape-based system, turn-around time for a complete report is substantially shorter with the Philips system than the tape-based system.

A brain gain with a brain drain

"We study human capital depletion and formation in an economy open to out-migration, as opposed to an economy which is closed. Under the assumption of asymmetric information, the enlarged opportunities and the associated different structure of incentives can give rise to a brain gain in conjunction with a brain drain. Migration by high-skill members of its workforce notwithstanding, the home country can end up with a higher average level of human capital per worker."

Return and dynamics: the path of labor migration when workers differ in their skills and information is asymmetric

"An implementation of the theory of labor migration under asymmetric information shows that return migration arises from the reinstatement of informational symmetry which induces low-skill workers, who are no longer pooled with high-skill workers, to return. When workers in an occupation constitute more than two skill levels, say four (without loss of generality), the following patterns emerge: Migration is sequential, that is, it proceeds in waves. Each wave breaks into workers who return and workers who stay; within waves the returning migrants are the low-skill workers. The average skill level of migrants is rising in the order of their wave."

Birth weight and body mass index in childhood, adolescence, and adulthood as predictors of blood pressure at age 36

STUDY OBJECTIVE

The purpose of this study was to investigate the relation between blood pressure at age 36, and birth weight and body mass index (BMI) in childhood, adolescence and adulthood.

DESIGN

Prospective longitudinal survey over a period of 36 years in England, Scotland, and Wales.

PARTICIPANTS

A nationally representative sample consisting of 3332 men and women born in one week in March 1946. Altogether 82% of these subjects had complete data for the present analysis.

MAIN RESULTS

There was an inverse linear relation between birth weight and blood pressure at age 36. The relation between BMI and blood pressure at age 36 was initially inverse and became increasingly positive throughout life. Weight gain in childhood was positively associated with adult blood pressure, although less important than weight change in later life. The associations between blood pressure and birth weight, and blood pressure and adult BMI were independent, and together they accounted for no more than 4% of the variation in adult blood pressure. Both low birth weight (birth weight < or = 2.5kg) and high BMI at age 36 (BMI > 30kg/m2) were associated with hypertension (> 140/90mmHg), but the per cent population risk of hypertension attributable to low birth weight was less than 5%, and to high BMI less than 12%.

CONCLUSIONS

Low birth weight and high BMI at age 36 were independently related to high blood pressure. A reduction in the percentage of low birthweight babies born in the fourth decade of this century would only have a negligible effect on the incidence of adult hypertension 30-40 years later.

Equilibrium urban unemployment in developing countries: is migration the culprit?

"This paper challenges the prediction of Todaro's model of rural-to-urban migration that an 'increase in urban employment increases urban unemployed.' It is shown that if the urban demand for labor is isoelastic or inelastic, creation of urban jobs causes urban unemployment to decline and urban-to-rural migration to take place. Moveover, urban job creation always reduces the rate of urban unemployment. The paper then remodels the urban job search process and derives the result that equilibrium urban unemployment would not vanish even if the urban-rural wage gap were eliminated." The geographical focus is on developing countries.

The probability of return migration, migrants' work effort, and migrants' performance

"This paper demonstrates that differences in earnings between migrants and the native population may reflect differences in incentives rather than differences in characteristics. The analysis indicates that in the presence of a positive probability of return migration, migrants' work effort is higher than that of comparable native-born workers. This differential may explain why, even if all workers are perfectly homogeneous in skills, migrants often outperform the native-born workers in the receiving economy."

Weight and age at menarche

In the National Child Development Study (1958 cohort) information on their age at menarche and their weights and heights measured at 7, 11, and 16 years was available for 4427 girls. The distribution of age at menarche was not influenced by social class. Weight adjusted for height did not play an important part in the timing of sexual maturation of the girls in the study. Relative weight (weight expressed as a percentage of standard weight) at the ages of 7 and 11 years explained only 3.2%, and 4.9%, respectively of the variation in age at menarche, and changes in relative weight between these two ages accounted for 2%. Girls with early menarche were more likely to be overweight at ages 7, 11, and 16 years than those with late menarche, although early menarche was also reported by girls who were underweight or of average weight. These findings support the hypothesis that in well nourished populations the relation between menarche and body size is largely regulated by genetic factors and that nutrition is less important.

Relative deprivation and international migration

This article provides theoretical reasoning and empirical evidence that international migration decisions are influenced by relative as well as absolute income considerations. Potential gains in absolute income through migration are likely to play an important role in households' migration decisions, but international migration by household members who hold promise for success as labor migrants can also be an effective strategy to improve a household's income position relative to others in the household's reference group. The findings reported in this article provide empirical support for the hypothesis that relative deprivation plays a significant role in Mexico-to-U.S. migration decisions. The findings also suggest that this migration is an effective mechanism for achieving income gains in households that send migrants to the U.S. and that households wisely choose as migrants those of their members who are most likely to provide net income gains.

Labour migration as a response to relative deprivation

The relationship between labor migration and relative deprivation is examined. "We model migration from one reference group to another as a response to relative deprivation and satisfaction: We say that a strong incentive to migrate exists if relative deprivation decreases while satisfaction rises with migration and that a weak incentive exists if the individual increases or decreases his satisfaction and deprivation at the same time by migrating. We derive conditions under which different incentives, weak or strong, hold for different individuals.... Our analysis enables us to explain several perplexing migratory phenomena, identify income inequality as a distinct explanatory variable of migration and establish an incentive to migrate in situations where the utility-social welfare approach does not."

Congenital cytomegalovirus infection: a cause of sensorineural hearing loss

Prospective studies have suggested that about 108 children with congenital cytomegalovirus (CMV) infection and bilateral sensorineural hearing loss are born each year in England and Wales; this represents about 12% of all children with congenital sensorineural hearing loss. Over a nine year period 1644 children aged between 6 months and 4 years who were attending the Nuffield Hearing and Speech Centre were screened for CMV infection. The prevalence of CMV in the urine of children with sensorineural hearing loss but no immediate family history of deafness was nearly twice that (13%) found in other children with impaired hearing and those with normal hearing (7%). These findings indicate the importance of CMV as a cause of hearing loss.

Genetic heterogeneity in different BB rat subpopulations

Two different BB-rat subpopulations were followed over 7 inbred generations under identical environmental conditions: BB/OK as derived in 1983 from the original stock in Ottawa, BB/PhiK as derived in 1983 from a stock at the University of Pennsylvania, Philadelphia. They showed significant differences in incidence, age at onset, untreated survival time of diabetes, leucopenia and body weight gain. By crossing experiments these phenotypical differences could be attributed to a genetic diversity between the 2 subpopulations. It is concluded that this genetic diversity is based on the heterogeneity of the parental BB Wistar rat stock and that the genetic differentiation between subpopulations of a different history is favoured by the "bottle neck effect", selection, mutation and genetic drift. The study of defined subpopulations and of their genetic interaction will provide deeper insight into the mechanisms of inheritance of diabetes in different species.

In vitro and in vivo behaviour of rat islets of Langerhans treated with MHC antisera and complement

The in vitro and in vivo behaviour of rat islets of Langerhans pretreated with polyclonal MHC antisera and complement was investigated. Complement-dependent cytotoxicity against rat islets was mediated by the antisera which were either directed against all MHC products ("a anti-u") or against products of the B-region of rat MHC ("Ba anti-Bu"). There were only minor alterations in glucose-stimulated insulin secretion and in 3H-leucine incorporation into islet proteins and into (pro)insulin in the pretreated islets. The syngeneic transplantation of "Ba anti-Bu"-treated islets led to a permanent graft survival in all streptozotocin-diabetic rats but after "a anti-u"-pretreatment permanent graft survival was only achieved in 33% of the syngeneic recipients. It is concluded, that in the latter case a complement-dependent cytotoxicity is exerted against the islets which may not allow sufficient in vivo survival. Now it appears necessary to look for effects of pretreatment prior to an allogeneic transplantation.

Genetic studies of IDDM in BB rats: the incidence of diabetes in F2 and first backcross hybrids allows rejection of the recessive hypothesis

The BB rat spontaneously develops an IDDM with many analogies to human IDDM, i.e. the genetic basis is a puzzle, since more than one mode of inheritance of IDDM in BB rats has been proposed. These different proposals reflect the heterogeneity of BB rats used for genetic studies. This prompted us to investigate the inheritance of IDDM in two subpopulations of BB rats (BB/OK and BB/PhiK) by crossing studies with the production of (diabetic BB x LEW 1.A) F1, F2 generations and of first backcross hybrids onto BB (B1BB) and LEW.1A (B1A) rats respectively. Both BB rat subpopulations were different in origin, degree of inbreeding, incidence and age at onset of diabetes and in certain immunologic, metabolic and hematologic traits. All hybrids were serotyped and checked for diabetes by determination of urine and plasma glucose twice weekly up to an age of 200 days. None of the F1 and B1A hybrids developed diabetes. Some cases were observed in the F2 hybrids with a different incidence in the two subpopulations (2.3% in BB/OK, 11.0% in BB/PhiK). The percentage of diabetes in the B1BB hybrids was 13.8% (BB/OK) and 24.0% (BB/PhiK) respectively. All diabetic hybrids were characterized by at least one RT1uv haplotype which was derived from the original BB animals. These results demonstrated clearly (1) that the mode of inheritance depends on the genotype of the animals observed and (2) simple autosomal-recessive genetics cannot be accepted for BB rat diabetes.(ABSTRACT TRUNCATED AT 250 WORDS)

Inducing fertility change: a game-theoretic approach

This paper explores the inducement of fertility change in situations where actual fertility levels do not coincide with socially optimal fertility levels. The motivating example is that of higher than socially optimal levels of fertility in less developed countries (LDCs), but the approach is equally applicable to contexts of lower than socially optimal levels of fertility in developed countries. The paper proposes a prisoner's dilemma characterization of higher than socially optimal levels of fertility in LDCs and offers a resolution of the dilemma, and hence a possible route to fertility-reduction policies, through the generation of mutual altruism. The prisoner's dilemma characterization hinges on the assumption that there is some social sharing of the costs associated with a given level of fertility but less or none with respect to the benefits. The mutual altruism solution depends on representing an agent's preferences as a specific convex combination of his/her and the other agent's original utilities. The unique critical level of such altruism is identified and hence a stopping rule is provided. Several examples from the array of extensions and possible implications of this approach are discussed briefly.

Obesity in 16-year-olds assessed by relative weight and doctors' rating

Weights and heights at age 16 of 5652 boys and 5280 girls from the National Child Development Study (NCDS) were measured. At this examination, school medical officers rated the boys and girls into one of the following categories: grossly obese, moderately obese, normal, thin or very thin. A comparison is made between doctors' rating and assessment of obesity by relative weight (RW). Obesity was defined as RW greater than 120. Overall 803 (15.2 per cent) girls were rated obese by doctors compared with 469 (8.9 per cent) identified by RW. Only 414 (7.8 per cent) girls were considered obese by both methods. In boys the difference between the two methods was less marked. There were 362 (6.4 per cent) boys rated as obese by doctors, 404 (7.2 per cent) by relative weight and 262 (4.6 per cent) by both methods. The discrepancies demonstrate that one method of assessment cannot replace another. Doctors' rated considerably more girls than boys as obese. Although at this age girls were heavier than boys for a given height, the doctors' rating may also reflect the different attitudes towards obesity in men and women which are prevalent in our society. Without comparison with a more accurate measure of adiposity it is not possible to reach a definite conclusion as to whether clinical assessment, relative weight, or indeed both methods combined are the most suitable for identifying obese adolescents.

Labor migration and risk aversion in less developed countries

"In this paper we question the pioneering work of Todaro, which states that rural-to-urban labor migration in less developed countries (LDCs) is an individual response to a higher urban expected income. We demonstrate that rural-to-urban labor migration is perfectly rational even if urban expected income is lower than rural income. We achieve this under a set of fairly stringent conditions: an individual decision-making entity, a one-period planning horizon, and global risk aversion. We obtain the result that a small chance of reaping a high reward is sufficient to trigger rural-to-urban labor migration."

Major histocompatibility complex (MHC)-independent differences between diabetes-prone BB rats and their parental Wistar rat strain in some hematologic and metabolic traits

In connection with the fact that BB rats are homogeneous for haplotype RT1u and their parental Wistar rat stock is heterogenous for haplotypes RT1u and RT1a the influence of the RT1 haplotypes on some hematologic and metabolic traits was studied. The findings indicate marked differences between BB rats and their parental strain independent of haplotype RT1 so that the changed genetic background of the BB rat rather than the haplotype per se seems to be the reason for the differences observed.

Prevalence of obesity in British children born in 1946 and 1958

The prevalence of overweight at ages 7 and 11 years and in late adolescence was compared in two nationally representative cohorts of British children born in 1946 and 1958. Overweight was defined as weight that exceeded the standard weight for height, age, and sex by more than 20% (relative weight greater than 120%). The prevalence of overweight among 7 year olds born in 1958 was nearly twice that among those born in 1946. Changes in infant feeding practices, food supply, and level of physical activity might be responsible for this difference. By adolescence the prevalence of obesity in both cohorts had increased but the difference between cohorts had almost disappeared. Around 9% of adolescent girls and 7% of adolescent boys were overweight. If infant feeding practices have an influence on prevalence of overweight at 7 years the data from the two cohorts suggest that such an effect does not persist. In neither cohort was there a significant relation between the prevalence of obesity and social class in boys, but in girls the prevalence was higher among those from the lower socioeconomic groups. Correlation coefficients showing the strength of the relation between relative weights at different ages were remarkably similar for both cohorts. The risk of being obese later in childhood for those who had not been obese at the age of 7 was less than one in 10, whereas for those with a relative weight greater than 130% the risk exceeded six in 10.

The major histocompatibility complex and insulin-dependent diabetes in BB rats

The partially inbred strain of BB-Wistar rats showed a varying incidence of the insulin-dependent diabetes-like syndrome. The serological typing of a large sample of BB rats verified the homozygosity for the RTlu haplotype, whereas its parental non-inbred Wistar stock segregated for RTlu and RTla haplotypes. The histogenetical typing of BB rats by skin grafting showed a significantly prolonged rejection of grafts from RTla donors unusual in other RTlu recipients. The presumption of some recombinational or mutational events in the RTl haplotype of BB rats was not verified by the simple F1 skin grafting test from LEW.1U/RTlu standard/donors to F1/LEW X BB/recipients. Skin grafts survived permanently. When trying to get a clear-cut answer whether the RTlu haplotype is associated with the spontaneous occurrence of diabetes in F2/LEW X BB/ X /LEW X BB/hybrids, only 7.4% of RTlu homozygotes were found among 359 weaned animals. Moreover, the partial strain of BB rats became extinct with the F1 generation mainly due to an infection by the mycoplasma. A new sample of outbred BB rats with a low incidence of spontaneous diabetes was found as homogeneous for the RTlu haplotype, too. Preliminary results of typing these rats for the secondary antibody response to pig insulin indicate the low responsiveness contrary to the results given earlier for the RTlu typing strains as high responders. All these results support the idea that the RTlu haplotype of the BB rats might be a variant carrying some mutational change(s) at the RTl.B region.

On the optimal choice of capital intensity in LDCs with migration

"Sen's classic work on the choice of capital intensity of investment is generalized in the light of new theoretical developments and empirical findings concerning rural-to-urban migration in LDCs. This is done by explicitly incorporating a migration function into the basic choice model. Revised conditions for maximization of surplus are derived and compared with Sen's original condition. Some justification for the particular migration function used in the presence of risk-aversion is suggested."

Longitudinal study of obesity in the National Survey of Health and Development

In a nationally representative cohort of 5362 children born in one week in March 1946 weights and heights were recorded at 6, 7, 11, 14, 20, and 26 years. Overweight was defined as a weight that exceeded the standard weight for height, age, and sex by more than 20% (relative weight greater than 120%). The prevalence of overweight was 1.7% and 2.9% in boys and girls respectively at 6 years; 2.0% and 3.8% at 7 years; 6.4% and 9.6% at 11 years; 6.5% and 9.6% at 14 years; 5.4% and 6.5% at 20 years; and 12.3% and 11.2% at 26 years. The risk of being overweight in adulthood was related to the degree of overweight in childhood and was about four in 10 for overweight 7-year-olds. Analysis of the data in the reverse direction showed that 7% and 13% respectively of 26-year-old overweight men and women had been overweight at the age of 7. These results suggest that there is no optimal age during childhood for the prediction of overweight in adult life and that excessive weight gain may begin at any time. Overweight children are more likely to remain overweight than their contemporaries of normal weight are to become overweight.

Genetic definition of a further gene region and identification of at least three different histocompatibility genes in the rat major histocompatibility system

Two new recombinant haplotypes of the rat major histocompatibility system, RT1, have been detected in [LEW.1A (RT1a) x LEW.1W (RT1U)] x LEW.1N(RT1n) segregating hybrids. Recombinant r3 carries the RT1.A region (determining classical transplantation antigens) and the RT1.B region (determining strong mixed lymphocyte reactivity and genetic control of antipolypeptide immune responsiveness) of the RT1a parent, bur rejects RT1a skin grafts. Recombinant r4 carries the A and B regions of the RT1u parent, but rejects RT1u skin grafts. The two histocompatibility genes detected are allelic to each other. The relevant locus, designated as H-C, maps to the B-region side of the RT1 system and appears to mark a third RT1 gene region, RT1.C. Availability of haplotypes r3 and r4 allowed the definition of a histocompatibility locus in the B region, H-B. The products of H-C, H-B and of the previously described H-A gene vary in antigenic strength.