Early diagnosis of a vein of Galen aneurysm: report of a case

Congenital vascular malformation with an aneurysm of the vein of Galen is rarely seen, particularly in the prenatal period. With the advancement of diagnostic techniques such as ultrasonography, we were able to detect a case prenatally and to diagnose it postnatally.

A two-state recurrent stochastic model with time-dependent transition rates

The two-state recurrent stochastic model with time-independent transition rates is generalized to a model with time-dependent transition rates. The rates can be any general function of external time, that is, any general function of the calendar time in which the process unfolds. Formulas for the state transition probabilities, the proportion of individuals in a particular state at time t, the distribution function, and the expectation of the number of individuals in a particular state at time t are derived.

A true rate of population growth--Lotka's intrinsic rate of natural increase revisited

In this paper, Lotka's intrinsic rate of current population growth is evaluated. A new method of computing the net reproduction rate and a new rate of population growth are proposed. The proposed rate is the rate of growth of the female population per woman per year. The rate is positive, equal to zero, or negative as a population is increasing, remaining stationary, or decreasing. The rate for the 1987 U.S. white female population was R = -0.0037. This means that the white population was decreasing in 1987 and was losing 3.7 females for every 1000 women per year.

Enzyme loading in a solid support with nonuniform pore size distribution

The concept of pore size distribution is incorporated into the Clark model of enzyme immobilization in the present study. This refined model predicted that in the case of small harmonic pore radius with the same surface area and porosity of the support, more enzyme could be loaded in a support with nonuniform pores than that with uniform pores. In comparing the enzyme loading efficiency of the support with two different pore size distributions, the one with Gaussian distribution had the greater amount of enzyme immobilized than the other one with Rajagopalan's distribution. Furthermore, more enzyme could be loaded in a support with wider Gaussian pore size distribution than that with narrower distribution. The immobilized enzyme profile in the solid support with pore size distribution displayed a stepwise pattern which differed appreciably from the sigmoidal profile predicted for the support with uniform pore size. This stepwise enzyme distribution profile became sigmoidal with decreasing h(T) or increasing k. The new model could be used for designing protocols for an enzyme immobilization process.

A survival model and estimation of time to tumor

In this paper we introduce a stochastic model of survival distribution, where the mortality intensity is a function of the accumulated effect of an individual's continuous exposure to toxic material in the environment (absorbing coefficient) and his biological reaction to the toxin absorbed (discharging coefficient). Formulas for the density function, the distribution function, and the expectation of lifetime are presented. The paper also includes special cases where there is a change in exposure level or exposure is discontinued or exposure is discrete in time. The model is then applied to the NCTR's serial sacrifice experimental study on mice fed 2-AAF, including some mice whose feeding was discontinued. The random variable here is the time to tumor. The chi-square test shows a good fit of the model to the data (P = 0.365). In addition to the parameters and their standard errors, estimates are computed for the expectation, variance, and percentiles of time to tumor, and for the age-specific cancer incidence rates. Confidence intervals for the parameters are also given.

Phospholipids and fatty acid profile of brain synaptosomal membrane from normotensive and hypertensive rats

1. The main synaptosomal membrane phospholipids and their acyl group profiles, from 3-4 month-old spontaneously hypertensive rats (SHR), were compared with those of age-matched normotensive Wistar Kyoto (WKY) rats. 2. The contents of the main or total phospholipids were not found to be significantly different between these two groups. It was also true for the membrane cholesterol contents in these two groups. 3. The acyl groups of the main phospholipids from hypertensive rats were significantly higher in the saturated fatty acids: such as palmitic acid or stearic acid, and lower in polyunsaturated fatty acids: such as undecylenic acid or docosahexaenoic acid, when compared to the corresponding normotensive controls. 4. The differences in the acyl group profile of the brain membrane phospholipids of the hypertensive rats seem to reflect an abnormality in the genetically related lipolytic process.

On maximum likelihood solutions for exponential survival models

"Stochastic survival models which adjust for covariate information have been developed by Beck (1979). These models can include one or two living states and several competing death states. The transitions between stages are assumed irreversible and the transition intensity functions are assumed to be independent of time but dependent upon the covariates." Explicit solutions of the maximum likelihood equations for such models when there are one or two dichotomous covariates are presented. Applications of these models to the case of heart transplants and lung cancer are discussed, and survival in two or four groups is compared. (summary in FRE)

Histocompatibility antigens controlled by the I region of the murine H-2 complex. II. K/D region compatibility is not required for I-region cell-mediated lymphocytotoxicity

In the cell-mediated lymphocytotoxicity assay, A.TH effector cells sensitized to A.TL lymphocytes lyse not only A.B10.AQR effector cells lyse B10.BR and B10.BYR target cells in addition to B10.AQR cells. These findings indicate that for CML to occur across the IA region barrier, compatibility at K or D regions is not required.

Ability of H-2 regions to induce graft-vs-host disease

Individual young adult F1 hybrid mice were irradiated with 500 R and 24 hr later injected with 5 X 10(7) spleen cells obtained from a sex-matched parental-strain donor. The injected animals were then followed for a period of 3 months and loss of body weight, mortality rate, and other signs of fatal graft-vs-host disease (GVHD) were recorded. The donor-recipient strain combinations were selected in such a way as to provide genetic differences in the entire H-2 complex, the K or D regions alone, the K or the D end, and the central (I) regions alone. The data obtained on only few combinations indicate that strong GVHD (100% mortality rate within the first month after the injection) occurs only in those donor-recipient combinations which differ in the entire H-2 complex or in the K end (K + I regions). Much weaker GVHD (mortality rate of only 50% or less and death of individual mice spread over the entire observation period) is observed when the donor and the host differ in either the K, I, or D region alone. The degree of GVHD induced by three regions, when taken singularly, is about the same. Surprisingly, the K-region GVHD was somewhat stronger in combinations of mutant strains in comparison with recombinant-strain combinations.

Making annual indexes of health

A discrete-state, continuous-time Markov model of health states and state transition probabilities is outlined as the basis of a health index that would reflect the annual health distribution and expected health changes of a population. The final index is an additive one, summing expected durations of the various health states over the entire population sample. The weights attached to the expected durations are derived from the instantaneous incidence rates, or intensity functions, that define the transition probabilities. A general procedure for collecting data during overlapping 6-week periods from numerous population subsamples is described.