[Mathematical model of a two level ecosystem]

The model which consists of two trophical levels is developed. The species here are connected by "pray--predator" relationship. If one supposes rather narrow specialisation of predator and introduces the "ecological space", the model which was preliminary recorded as a system of common differential equations of great dimension can be modified to the system of two non-linear equations in partial derivatives. Linear approach was investigated analytically, the previous nonlinear problem was calculated on a computer. The most interesting result here is an appearance of space--time oscillations in the system, which can be regarded as the first stages of ecological succession.

Pattern analysis in the study of infantile diarrhoea and other epidemiological problems

The patterns imposed on records of epidemiological variables by spatial, temporal, and other factors demand a special approach for their identification, characterization, and interpretation. Over the last 10 years, a methodology based on pattern analysis has been developed and put to the test in elucidating selected epidemiological problems. The aim of this approach is to link the pattern or its detailed features to factors likely to be important in understanding the origins of the disease and the mechanisms underlying its occurrence; such knowledge may in turn suggest methods that can be used to control the disease. Pattern analysis provides a battery of techniques that can greatly enhance the cost-effectiveness of epidemiological investigations. To exemplify these techniques, the applications of pattern analysis in the study of the infantile diarrhoeal complex and in elucidating the epidemic spread of wildlife rabies are described. Some other examples are mentioned briefly and comments are made on the more important techniques available.

Plasma high-density lipoproteins and ischemic heart disease: studies in a large kindred with familial hypercholesterolemia

The expression of ischemic heart disease was studied in a large kindred with familial hypercholesterolemia. Tendon xanthomas, multiple generation transmission, and the appearance of bimodality in the distributions of total and low-density lipoprotein cholesterol were found. The segregation ratio was 0.9 in females and 0.43 in males, a difference first apparent during adolescence. The upper quartile of total and low-density lipoprotein cholesterol contained all but two cases of ischemic disease, whereas the lower quartile of high-density lipoprotein cholesterol contained one half of the cases. The ratio of high- to low-density lipoprotein cholesterol (range, 0.06 to 1.6) was less than or equal to 0.20 in each patient with ischemic disease. The association of a low level of high-density lipoprotein cholesterol with ischemic disease persisted after adjustment for differences in other lipids and lipoproteins. A low level of high-density lipoprotein cholesterol, as well as a high level of low-density lipoprotein cholesterol, may influence the development of ischemic heart disease in this disorder.

Geographical distribution of Burkitt's lymphoma in Nigeria

Eight hundred and eighty cases of Burkitt's lymphoma recorded in the Cancer Registry, University College Hospital (U.C.H.) Ibadan during a fifteen-year period (1961-1975) were reviewed. The geographical locations ascertained represent 87 cities or towns. No case of Burkitt's lymphoma has been reported from areas above latitude 11 degrees north of the equator which are essentially desert areas. There is no explanation for the yearly and monthly variations in the number of cases reported. A case-detection programme probably will give a true picture of the geographical distribution of the disease including possible 'clustering of cases in space and time'.

Nosocomial infections in a community hospital: 1972 through 1976

Of 78,057 patients discharged from a community hospital from 1972 through 1976, nosocomial infections developed in 3.58 per cent. Nosocomial infections of all types were 13.2 times more frequent for patients with rapidly fatal underlying illness and 3.4 times more frequent for patients with ultimately fatal underlying illness than in cases of nonfatal underlying illness. Outbreaks of epidemics or clusters of infections caused by the same organism were distinctly uncommon. These outbreaks accounted for only 49 of the 2,798 nosocomial infections found. No distinct trends, either increases or decreases, of infection rates by pathogen, site of infection, or service were noted during the study period. Sensitivity of the common pathogens to antibiotics also remained stable.

Multiple sclerosis and canine distemper in Iceland

Iceland offers a favourable opportunity to examine the suggested relationship between canine distemper and multiple sclerosis. Distemper is not enzootic in Iceland and distemper immunisation is not practised. However, importations result in occasional epizootics, three of which have occurred since 1909. Careful enumeration of multiple sclerosis indicates that there were 129 cases during the period 1946--65. When these cases are subdivided into six regions, by place of birth, regional period-prevalence rates were highest in two regions partially involved by distemper only once in the past 70 years. Also, there was substantial prevalence in a third region, encompassing Reykjavik, where the dog population has been kept very low for over 50 years. The Icelandic experience indicates that multiple sclerosis can occur at high incidence in the virtual absence of canine distemper or in the presence of a very small dog population.

A detection algorithm for multiform premature ventricular contractions

This paper reports an algorithm developed to identify and quantify multiform PVCs. The algorithm clusters PVCs of similar morphology using a combination of time-domain and frequency-domain analysis. Initially, PVCs are grouped together on the basis of four time-domain-based morphological feature measurements. However, these time-domain-based clusters many times are nonunique because commonly encountered signal changes can cause substantial variations in the feature measurements of clinically similar beats. These redundant clusters are consolidated using two frequency-domain parameters: The First Spectral Moment (FSM) (center of gravity) of the amplitude spectrum, and the 5-Hz phase angle.

A two-dimensional clustering technique for identification of multiform ventricular complexes

A computer algorithm for the identification of multiform ectopic ventricular complexes in 24-hour ambulatory electrocardiographic recordings is described. The clustering technique established regions, based on R-R interval and ST-segment slope, in a two-dimensional probability space based on the fit of each ventricular complex. The boundaries of any overlapping regions are analyzed using a Bayesian decision rule to minimize misclassification.

Multivariate analyses of the MMPI profiles of low back pain patients

A multivariate clustering procedure was used to identify replicable, homogeneous MMPI profile subgroups among three independent cohorts of male (N = 233) and female (N = 315) low back pain ((LBP) patients. Three subgroups were replicated across all male cohorts and four subgroups were replicated across all female cohorts. Multiple discriminant analysis showed that for both male and female patients between-subgroup variability was significantly greater than within-subgroup variability. The results suggest that LBP patients may not be solely characterized by MMPI profiles featuring the "conversion V" configuration. Examination of the profile subgroups also suggests there may be distinct, pain-related, behavioral attributes associated with each subgroup which might have important implications for practitioners' choice of treatment modalities. Suggestions are made for research regarding the development of specific, optimal treatments for various LBP patient subgroups.

Enterobacter aerogenes primary bacteremia in pediatric patients

Enterobacter aerogenes bacteremia associated with the infusion of contaminated admixed intravenous (IV) fluid occurred in seven patients in a pediatric hospital over a five-day period. Clinical illness was characterized by spiking fever in all patients. The temporal clustering of cases allowed for rapid recognition of the problem. The primary control measure was the prompt replacement of the IV fluids, although IV antibiotics were also administered. Hospital pharmacy practices for admixing IV solutions should follow published recommendations to minimize this source of potential contamination of fluids.

Behavioural syndromes identified by cluster analysis in a sample of 100 severely and profoundly retarded adults

Very little is known about psychiatric disorders in severely and profoundly retarded adults. We have investigated these disorders by systematically recording and collecting data about the behaviour of 100 severely and profoundly retarded hospitalized adults and subjecting the data thus derived to cluster analysis. Eight clusters were isolated. The clinical psychiatric significance of these clusters is discussed and their relationship to cause retardation, duration of stay in hospital and visiting is considered. A diagnostic framework for psychiatric disorder in severely and profoundly retarded adults is put forward and some possible treatment approaches are suggested.

A cluster of Hodgkin's disease in a small community: evidence for environmental factors

A cluster of Hodgkin's disease (HD) cases occurred in a small rural town of 1250 people. Ten cases of HD and three cases of non-Hodgkin's lymphoma were identified within or linked to this town since 1954. This town therefore had an average annual incidence and mortality for HD of 29.3 and 16.7 cases per 100,000 population, respectively. Most cases of HD demonstrated case-contact associations, and a distinct geographic distribution. The data suggested that there was an environmental agent responsible for the elevated rates of HD. One unique aspect of this cluster is that this town has only one industry, a large grain elevator. The cases closely surrounded this elevator. We postulate that residents of the town are subject to chronic immune stimulation from mitogenic substances in this environment. These agents may alter immunity in the residents of this community and predispose them to acquiring HD.

Epidemiology of Guillain-Barré syndrome

From 1969 through 1972, a nationwide search for cases of Guillain-Barré syndrome (GBS) is Israel revealed 89 patients. The average annual age-adjusted incidence was 0.75 per 10(5) persons. Overall incidence of the syndrome was similar in Jewish groups of diverse ethnic backgrounds. Arabs had a lower overall incidence than Jews (0.46 per 10(5) persons), perhaps attributable to fewer Arabs at risk in older age groups. Peaks of incidence occurred among individuals over 60 and under 4 years of age when all cases were combined. No clear seasonal or geographic clustering of GBS was evident in Israel during the 4 years of this study. The incidence of GBS in the present study agrees with previous population-based estimates.

Multivariate statistical methods and problems of classification in psychiatry

This paper is concerned with the use of multivariate statistical methods in relation to classification in psychiatry. There are two aspects of classification: the classification of symptoms to form syndromes and of patients into diagnostic groups. Critical papers are reviewed, and proposed severe limitations on the methods answered. The use of multivariate methods has increased objectivity and agreement between investigators, but differences remain, largely on issues in statistical logic, which must be resolved.

Paralytic poliomyelitis in England and Wales 1976-7

In 1976-7 26 cases of paralytic poliomyelitis were notified, of which 6 were vaccine-associated. 16 of the 20 non-vaccine-associated cases were due to type-u poliovirus, the type usually associated with outbreaks. The most important factor in the increase was the occurrence of poliomyelitis in unvaccinated persons.

Variola minor in Bragança Paulista County, 1956. Distribution of onset of cases in the two schools including most school children with variola

Class attendance during illness was confirmed for numerous pupils of two schools. Successive generations whose median cases were separated by an interval consistent with the "serial interval" of variola minor were clearly found in the epidemic curve for II of the 29 classes with cases from both schools. Twenty two other classes had no case at all.

Familial clustering and immune response in family contacts of patients with HBsAg-positive liver cirrhosis

Families of 11 patients with hepatitis B surface antigen (HBsAg)-positive cirrhosis were studied to evaluate the immunologic correlates and extent of intrafamilial HBsAg clustering. Of 76 family contacts, 12 were identified to be asymptomatic carriers of HBsAg and two were diagnosed to have HSsAg-positive cirrhosis. The over-all HBsAg prevalence for the 76 contacts was 18% and that for all 87 members studied 29.0%. Serologic evidence of hepatitis B virus (HBV) infection (either HBsAg, anti-HBs, or both) was detected in 59% of all family members. HBsAg was more prevalent in males (47%) compared with females (16%), and anti-HBs was more prevalent in females (42%) compared with males (18%). Evidence of an immunologic response in clinically unaffected HBsAg-negative family contacts consisted of elevated serum IgG levels (mean 1660 mg/100 ml) and increased prevalence of anti-smooth muscle and antimitochondrial antibodies (16% and 6%, respectively). The prevalence of one or more autoantibodies in all HBsAg-negative family contacts was 20%, and it was higher in females (25%) than in males (13%). The present study demonstrates that HBsAg clustering occurs in families of patients with cirrhosis in the Jerusalem area and indicates that HBsAg-negative family contacts may have increased B-cell activity.