Showing papers by "University of Illinois at Chicago published in 1987"

Application of model-selection criteria to some problems in multivariate analysis

Abstract: A review of model-selection criteria is presented, with a view toward showing their similarities. It is suggested that some problems treated by sequences of hypothesis tests may be more expeditiously treated by the application of model-selection criteria. Consideration is given to application of model-selection criteria to some problems of multivariate analysis, especially the clustering of variables, factor analysis and, more generally, describing a complex of variables.

Studies of multiphoton production of vacuum-ultraviolet radiation in the rare gases

Abstract: Measurements of the vacuum-ultraviolet (<80-nm) radiation produced by intense ultraviolet (248-nm) irradiation (1015–1016 W/cm2) of rare gases have revealed the copious presence of both harmonic radiation and fluorescence from excited levels. The highest harmonic observed was the seventeenth (14.6 nm) in Ne, the shortest wavelength ever produced by that means. Strong fluorescence was seen from ions of Ar, Kr, and Xe, with the shortest wavelengths observed being below 12 nm. Furthermore, radiation from inner-shell excited configurations in Xe, specifically the 4d95s5p → 4d105s manifold of Xe7+ at ~17.7 nm, was detected. These experimental findings, in alliance with other studies concerning multielectron processes, give evidence for a role of electron correlations in a direct nonlinear process of inner-shell excitation.

Medicinal plants in therapy.

Abstract: One of the prerequisites for the success of primary health care is the availability and use of suitable drugs. Plants have always been a common source of medicaments, either in the form of traditional preparations or as pure active principles. It is thus reasonable for decision-makers to identify locally available plants or plant extracts that could usefully be added to the national list of drugs, or that could even replace some pharmaceutical preparations that need to be purchased and imported. This update article presents a list of plant-derived drugs, with the names of the plant sources, and their actions or uses in therapy.

Deterrence or Escalation?: The Puzzle of Aggregate Studies of Repression and Dissent

Abstract: Aggregate data studies of domestic political conflict have used an Action-Reaction (AR) model that has produced contradictory findings about the repression/dissent nexus: Repression by regimes may either increase or decrease dissent by opposition groups. To clarify these findings I propose an alternative Rational Actor (RA) model from which are derived three propositions. (1) An increase in a government's repression of nonviolence will reduce the nonviolent activities of an opposition group but increase its violent activities. (2) The balance of effects, that is, whether an increase in the regime's repression increases or decreases the opposition group's total dissident activities, depends upon the government's accommodative policy to the group. (3) Consistent government accommodative and repressive policies reduce dissent; inconsistent policies increase dissent. The RA model thus accounts for the contradictory findings produced by the AR-based aggregate data studies of repression and dissent.

Segmentation and Classification of Range Images

Abstract: The recognition of objects in three-dimensional space is a desirable capability of a computer vision system. Range images, which directly measure 3-D surface coordinates of a scene, are well suited for this task. In this paper we report a procedure to detect connected planar, convex, and concave surfaces of 3-D objects. This is accomplished in three stages. The first stage segments the range image into ``surface patches'' by a square error criterion clustering algorithm using surface points and associated surface normals. The second stage classifies these patches as planar, convex, or concave based on a non-parametric statistical test for trend, curvature values, and eigenvalue analysis. In the final stage, boundaries between adjacent surface patches are classified as crease or noncrease edges, and this information is used to merge compatible patches to produce reasonable faces of the object(s). This procedure has been successfully applied to a large number of real and synthetic images, four of which we present in this paper.

Proliferation, Hormonal Responsiveness, and Estrogen Receptor Content of MCF-7 Human Breast Cancer Cells Grown in the Short-Term and Long-Term Absence of Estrogens

Abstract: We have examined the effect of short-term and long-term growth in the absence of estrogens on the proliferation rate and estrogen and antiestrogen responsiveness of MCF-7 human breast cancer cells. The removal of phenol red, the pH indicator in tissue culture medium that is weakly estrogenic (Y. Berthois et al., Proc. Natl. Acad. Sci. USA, 83:2496-2500, 1986), immediately slows the cell proliferation rate, and MCF-7 cells grown in phenol red-free medium with charcoal dextran-treated serum for periods up to 1 mo maintain this reduced rate of cell proliferation. In these short-term phenol red-withdrawn cells, estradiol stimulates proliferation markedly and reproducibly, and antiestrogens inhibit estrogen-stimulated proliferation. Antiestrogens by themselves appear as partial agonists/antagonists; at low concentrations they stimulate proliferation weakly, but they show no stimulation at the high concentrations where they fully inhibit estrogen-stimulated proliferation. In contrast to the short-term phenol red-withdrawn cells, cells maintained for several months (5 to 6 mo) in the apparently complete absence of estrogens (no phenol red, with charcoal dextran-treated calf serum) show a markedly increased basal rate of cell proliferation; estradiol is unable to increase this rate of proliferation further, but antiestrogens are able to decrease proliferation. This change in growth pattern is associated with a 3-fold increase in cellular estrogen receptor levels. Despite their differing basal growth rates, cells grown in either the short-term (less than 1 mo) or long-term (greater than 6 mo) absence of estrogens both have progesterone receptor levels that are very low and, in both cases, estradiol increases progesterone receptor levels markedly. Thus, under long-term estrogen-free conditions, there is a dissociation between the stimulation of cell proliferation and of specific protein synthesis (progesterone receptor) by estrogen. The increase in the cell proliferation rate observed in cells grown in the long-term absence of estrogen may reflect altered regulation of growth factor production or altered sensitivity to growth factors in the medium or produced by the cells themselves. Hence, these breast cancer cells adapt significantly to long-term growth in estrogen-free conditions, an observation that may be relevant to understanding the growth of hormone-responsive human breast cancers in vivo.

High-dose calcium channel-blocking therapy for primary pulmonary hypertension: evidence for long-term reduction in pulmonary arterial pressure and regression of right ventricular hypertrophy

Abstract: In an attempt to produce substantial reductions in pulmonary arterial pressure and pulmonary vascular resistance in patients with primary pulmonary hypertension, a new treatment strategy using high doses of calcium channel-blocking drugs was developed. Thirteen patients were given an initial test dose of 60 mg diltiazem or 20 mg nifedipine followed by consecutive hourly doses until a 50% fall in pulmonary vascular resistance and 33% fall in pulmonary arterial pressure was achieved or untoward side effects developed. The initial drug challenges failed to produce significant reductions in mean pulmonary arterial pressure or pulmonary vascular resistance. In eight of 13 patients, continued hourly doses produced a reduction in mean pulmonary arterial pressure of 48% (61 to 35 mm Hg, p less than .01) and a reduction in pulmonary vascular resistance of 60% (15 to 6 units, p less than .01). These patients were discharged on high-dose (up to 720 mg/day diltiazem or 240 mg/day nifedipine) calcium channel-blocking drugs as long-term therapy. Five patients have returned for restudy after 1 year. In four of five the reductions in pulmonary arterial pressure and pulmonary vascular resistance were sustained and were associated with regression of right ventricular hypertrophy as assessed by electrocardiography and echocardiography. One patient who reduced her dose to a conventional level had a return of her pulmonary arterial pressure and pulmonary vascular resistance toward previous levels. We conclude that substantial reductions in pulmonary arterial pressure and pulmonary vascular resistance that are associated with regression of right ventricular hypertrophy are possible in some patients with primary pulmonary hypertension by use of calcium channel-blocking drugs.(ABSTRACT TRUNCATED AT 250 WORDS)

The measurement of performance in childhood cancer patients.

Abstract: The performance status of the child with cancer is an important outcome consideration in pediatric oncology research and practice. However, no single measure for children has been available. This is a report of the development and standardization of such a scale. The play-performance scale for children is a parent-rated instrument which records usual play activity as the index of performance. Performance status ratings were obtained on three groups of children: patients (n = 98), patients' siblings (n = 29), and an independent sample of hospital employees' children (n = 40). Children with all types and stages of childhood malignant neoplasms were represented. Test results established the parent as a competent, reliable rater and demonstrated the validity of the scale. Interrater reliability was examined using correlational statistics and percentage agreement. Agreement between parents was good, and there were no systematic rater biases. In addition, parents' ratings significantly discriminated differences in levels of functioning (mean score, patients 75.4 versus siblings 97.4). Correlational and analysis of variance (ANOVA) procedures demonstrated that the play-performance scale was significantly related to the global performance measures of experienced clinicians and was sensitive to change. Inpatients received a mean score of 42.3, outpatients 90.7, and normals 98.2. These findings indicate that the scale is both feasible and effective. It is concise, can be administered repeatedly even to extremely ill patients, and uses parents as observer reporters. The play-performance scale for children provides quantifiable, reproducible, and meaningful data, which is necessary for effective monitoring and management of the child with cancer.

Anatomical and physiological characteristics of vestibular neurons mediating the vertical vestibulo‐ocular reflexes of the squirrel monkey

Abstract: The morphology of 35 vestibular neurons whose firing rate was related to vertical eye movements was studied by injection of horseradish peroxidase intracellularly into physiologically identified vestibular axons in alert squirrel monkeys. The intracellularly injected cells were readily classified into four main groups. One group of cells, down position-vestibular-pause neurons (down PVPs; N = 12), increased their firing rate during downward eye positions, paused during saccades, and were located in the medial vestibular nucleus (MV) and the adjacent ventrolateral vestibular nucleus (VLV). They had axons that crossed the midline and ascended in the medial longitudinal fasciculus (MLF) to terminate in the trochlear nucleus, the lateral aspect of the caudal oculomotor nucleus, and the dorsal aspect of the rostral oculomotor nucleus. A second group of cells (N = 15) were also located in the MV and VLV, but increased their firing rate during upward eye positions, and paused during saccades. These cells had axons that crossed the midline and ascended in the contralateral MLF to terminate in the medial aspect of the oculomotor nucleus. A third group of cells (N = 4) were located in the superior vestibular nucleus, generated bursts of spikes during upward saccades, and increased their tonic firing rate during upward eye positions. These cells had axons that ascended laterally to the ipsilateral MLF to terminate in regions of the trochlear and oculomotor nuclei similar to those in which down PVPs terminated. A fourth group of cells (N = 4), located in the VLV, had axons that projected to the spinal cord, although they had firing rates that were significantly correlated with vertical eye position. Electrical stimulation of the vestibular nerve evoked spikes at monosynaptic latencies in each of the above classes of cells, six of which were injected with horseradish peroxidase. Each group of cells had collateral projections to other areas of the brainstem. Some of the neurons that projected to the contralateral trochlear and oculomotor nuclei had collaterals that crossed the midline to terminate in the oculomotor nucleus ipsilateral to the soma, and some gave rise to small collaterals that terminated in the abducens nucleus. Other areas of the brainstem that received collateral inputs from neurons projecting to oculomotor and trochlear nuclei included the interstitial nucleus of Cajal, the caudal part of the dorsal raphe nucleus, the nucleus raphe obscurus, Roller's nucleus, the intermediate and caudal interstitial nuclei of the MLF, and the nucleus prepositus.

Threshold circuits of bounded depth

Abstract: We examine a powerful model of parallel computation: polynomial size threshold circuits of bounded depth (the gates compute threshold functions with polynomial weights). Lower bounds are given to separate polynomial size threshold circuits of depth 2 from polynomial size threshold circuits of depth 3, and from probabilistic polynomial size threshold circuits of depth 2. We also consider circuits of unreliable threshold gates, circuits of imprecise threshold gates and threshold quantifiers.

Oculoauriculovertebral dysplasia and variants: Phenotypic characteristics of 294 patients

Abstract: Here we describe the phenotypic characteristics of a single craniofacial clinic population of 294 individuals affected with oculoauriculovertebral dysplasia (OAV) and variants. To our knowledge, this is the largest population so described in the literature. The study population was divided into five subgroups based on the presence of combinations of minimal diagnostic criteria: microtia, mandibular hypoplasia, anomalies of the cervical spine and/or epibulbar or lipodermoids. The following data were recorded: sex (M:F 191:103); race (78% Caucasian); the presence of unilateral or bilateral microtia (193 unilateral, 98 bilateral); the presence of symmetric microtia in bilateral cases (34/98); the presence of mandibular hypoplasia ipsilateral or contralateral to the microtic ear or most severely microtic ear in bilateral cases (135/137 were ipsilateral in unilateral cases, 55/62 were ipsilateral in bilateral cases); the number of individuals with no other congenital anomaly in addition to the minimal diagnostic criteria (154/294), with only one other congenital anomaly (51/294), and with two or more other congenital anomalies (89/294); and the type of other congenital anomalies. Finally, we compared our results with other studies. Findings from our study include: mandibular asymmetry should be expected in patients with unilateral or bilateral microtia; bilateral involvement is frequent in patients with microtia; other malformations are seen frequently in all subgroups; anomalies of the cervical spine are more likely to be associated with other anomalies; and other malformations are seen in all systems and should be searched for to provide optimal management.

Reduced clearance rate of thyroxine-binding globulin (TBG) with increased sialylation: a mechanism for estrogen-induced elevation of serum TBG concentration.

Abstract: Hyperestrogenemic states, including pregnancy, cause an increase in serum T4-binding globulin (TBG) concentrations and an increase in the proportion of TBG molecules with greater anodal mobility on isoelectric focusing, indicating greater sialic acid content. The possible causal relationship between the degree of sialylation and accumulation of TBG in serum was explored by measuring the in vivo half-lives (t1/2) of TBGs with different isoelectric points. TBG in unfractionated serum and its major peaks, isolated by chromatofocusing and defined by their isoelectric points on isoelectric focusing were each injected iv into rats. The resulting TBG concentrations, measured by specific RIA in serum samples obtained at intervals after injection, were used for the calculation of the t1/2. TBG in serum from a pregnant woman had a significantly longer t1/2 of 17.2 +/- 1.2 h (mean +/- SD) compared to those of 13.3 +/- 1.5 and 12.9 +/- 0.9 h for TBG in serum from a man and a nonpregnant woman, respectively. TBG peaks II, III, IV, and V, with increasing anodal mobility, had progressively longer t1/2 values of 11, 13, 15, and 33 h, respectively. However, TBG peaks of the same mobility on IEF isolated from serum of pregnant or nonpregnant subjects had similar t1/2 values. Neither the TBG concentration nor estrogen had a direct effect on the rate of TBG clearance. Indeed, the t1/2 of TBG from a subject with inherited TBG excess was not different from that of TBG from a nonpregnant woman or a man. Chronic treatment of rats with estradiol did not alter the rate of clearance of injected human TBG. Finally, the more heavily sialylated anodal bands of purified but unfractionated serum TBG, analyzed by Western blots, survived longer in the circulation of a rat. These results indicate that the rate of in vivo metabolism of TBG is dependent on its sialic acid content. The increased proportion of TBG molecules with higher sialic acid content thus contributes to the increase in the serum TBG concentration in hyperestrogenemic states.

The effects of excitatory amino acids on intracellular calcium in single mouse striatal neurons in vitro.

Abstract: Using microspectrofluorimetry and the calcium-sensitive dye fura-2, we examined the effect of excitatory amino acids on [Ca2+]i in single striatal neurons in vitro. N-methyl-D-aspartic acid (NMDA) produced rapid increases in [Ca2+]i. These were blocked by DL-2-amino-5-phosphonovaleric acid (AP5), by Mg2+, by phencyclidine, and by MK801. The block produced by Mg2+ and MK801 could be relieved by depolarizing cells with veratridine. When external Ca2+ was removed, NMDA no longer increased [Ca2+]i. Furthermore, the effects of NMDA were not blocked by concentrations of La3+ that blocked depolarization induced rises in [Ca2+]i. Substitution of Na+o by Li+ did not block the effects of NMDA. Concentrations of L-glutamate greater than or equal to 10(-6) M also increased [Ca2+]i. The effects of moderate concentrations of glutamate were blocked by AP5 but not by La3+ or by substitution of Na+ by Li+. The effects of glutamate were blocked by removal of external Ca2+ but were not blocked by concentrations of Mg2+ or MK801 that completely blocked the effects of NMDA. The glutamate analogs kainic acid (KA) and quisqualic acid also increased [Ca2+]i. The effects of KA were blocked by removal of external Ca2+ but not by La3+, Mg2+, MK801, or replacement of Na+ by Li+. Although AP5 was able to block the effects of KA partially, very high concentrations were required. These results may be explained by considering the properties of glutamate-receptor-linked ionophores. Excitatory amino acid induced increases in [Ca2+]i are consistent with the possibility that Ca2+ mediates excitatory amino acid induced neuronal degeneration.

Calculation and experimental validation of induced currents on coupled wires in an arbitrary shaped cavity

Abstract: An efficient numerical technique is presented for the calculation of induced electric currents on coupled wires and multiconductor bundles placed in an arbitrary shaped cavity and excited by an external incident plane wave. The method is based upon the finite-difference time-domain (FD-TD) formulation. The concept of equivalent radius is used to replace wire bundles with single wires in the FD-TD model. Then, the radius of the equivalent wire is accounted by a modified FD-TD time-stepping expression (based on a Faraday's law contour-path formulation) for the looping magnetic fields adjacent to the wire. FD-TD computed fields at a virtual surface fully enclosing the equivalent wire are then obtained, permitting calculation of the currents on the wires of the original bundle using a standard electric field integral equation (EFIE). Substantial analytical and experimental validations are reported for both time-harmonic and broad-band excitations of wires in free space and in a high- Q metal cavity.

Temporal modulation sensitivity and pulse-detection thresholds for chromatic and luminance perturbations.

Abstract: We studied temporal processing of chromatic and luminance perturbations of a 600-nm field, measuring both modulation sensitivity (sinusoidal frequencies from 0.25 to 40 Hz) and pulse-detection thresholds (pulse durations from 5 to 2560 msec) for mean luminances of 0.9 to 900 Td and field sizes of 0.5 degrees to 8 degrees. Chromatic stimuli were produced by antiphase modulation of lights matched by heterochromatic flicker photometry. Both mean luminance and field size affected sensitivity, and the magnitude of field-size effects increased with mean luminance. We derived both luminance and chromatic impulse response functions for each set of experimental conditions, using the modulation-sensitivity data. At high mean luminances and large field sizes the chromatic impulse response functions are complex, suggesting contributions from both chromatic and luminance mechanisms. Pulse-detection data were fitted by a peak detector model based on these impulse response functions.

Enhanced critical magnetization currents due to fast neutron irradiation in single-crystal Y Ba 2 Cu 3 O 7 − δ

Abstract: Magnetization measurements were performed on single crystals of $\mathrm{Y}{\mathrm{Ba}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{7\ensuremath{-}\ensuremath{\delta}}$ to study the effect of fast neutron irradiation on flux pinning and the critical magnetization current. Neutron irradiation up to a fluence of 8.16\ifmmode\times\else\texttimes\fi{}${10}^{17}$ n/${\mathrm{cm}}^{2}$ systematically enhanced the magnitude and reduced the anisotropy of the critical magnetization current compared to unirradiated samples. The largest increases in the critical magnetization current occurred at 77 K. There was a slight linear decrease in the transition temperature with neutron fluence.

Beyond Anomalies: Rethinking the Conflict Perspective on Race and Criminal Punishment

Abstract: Research on race and punishment for crime has produced inconsistent findings. Most previous reviews of the literature have been focused primarily on the numerous methodological flaws that may give rise to such inconsistencies. In this paper I suggest that inconsistent or anomalous findings in this area of research may also result from problems of conceptualization and theory. More specifically, it is argued that the conflict perspective must be substantially revised to begin to account for various anomalies observed by empirical researchers. Such a need for revision is the consequence of both problems in the original formulation of the perspective and its oversimplification within the empirical literature. One of the most widely debated issues in the criminological literature is whether there is racial bias in the administration of justice. In addition to numerous empirical investigations, there have been efforts in recent years to review previous studies and to determine where the weight of the evidence lies (Green 1971; Hagan 1974; Hagan and Bumiller 1983; Hardy 1983; Kleck 1981; Spohn et al. 1981-82). As in other areas of social research, most studies of racial bias in the administration of justice involve black-white comparisons. Reviews of empirical investigations have shown a large number of these studies to report significantly greater rates and levels of punishment for blacks than for whites.1 Others report no significant differences between the races. Still others find that in certain instances, whites receive significantly more punishment for crime than do blacks (e.g., Bernstein et al. 1977; Bullock 1961; Gibson 1978; Levin 1972). This latter finding is often described as an anomaly or inconsistency given the theoretical model that has guided research on this topic. Released time to prepare this paper was provided by the R. J. Reynolds Foundation and by the National Science Foundation, Grant No. RII-8421196. I thank John Hagan, Michael Radelet, and anonymous referees for their helpful comments on earlier drafts. Address correspondence to the author, Black Studies Program and Department of Sociology, University of Illinois, Chicago, IL 60680. ? 1987 The University of North Carolina Press

Fish oil inhibits development of atherosclerosis in rhesus monkeys.

Abstract: The effect of feeding fish oil (Menhaden) on the progression of rhesus monkey atherosclerosis was determined by feeding diets containing 2% cholesterol and either 25% coconut oil (Group I), 25% fish oil/coconut oil (1:1) (Group II), or 25% fish oil/coconut oil (3:1) (Group III) for 12 months (n = 8/group). The average serum cholesterol levels were 875 mg/dl for Group I, 463 mg/dl for Group II, and 405 mg/dl for Group III. HDL cholesterol levels were 49 mg/dl for Group I, 29 mg/dl for Group II, and 20 mg/dl for Group III. An average of 79% of the aortic intima was involved with atherosclerosis in Group I, 48% in Group II, and 36% in Group III. The aortas of both fish-oil groups (II or III) contained significantly less cholesterol (total, free, and esterified), as well as less acid lipase, cholesteryl esterase, and ACAT activities when compared to the coconut-oil group (I) (p less than 0.05). Microscopically, the aortic and carotid artery lesions were smaller in cross-sectional area and in thickness, and contained less macrophages in the fish-oil groups (II and III) when compared to the coconut-oil group (I) (p less than 0.05). This protective effect was not consistently enhanced by increasing the proportion of fish oil to 3:1 (Group III) over 1:1 (Group II). The results indicate that fish oil-containing diets reduce serum cholesterol levels and inhibit atherosclerosis even in the face of lowered HDL cholesterol levels when compared to a pure coconut oil/cholesterol diet in rhesus monkeys. Therefore, fish-oil diets exert effective protective control of progression of atherosclerosis during severe atherogenic stimuli.

Forced convection in a duct partially filled with a porous material

Abstract: This paper presents a theoretical study of fully developed forced convection in a channel partially filled with a porous matrix. The matrix is attached at the channel wall and extends inward, toward the centerline. Two channel configurations are investigated, namely, parallel plates and circular pipe. For each channel configuration, both the case of constant wall heat flux and constant wall temperature were studied. The main novel feature of this study is that it takes into account the flow inside the porous region and determines the effect of this flow on the heat exchange between the wall and the fluid in the channel. The Brinkman flow model which has been proven appropriate for flows in sparsely packed porous media and for flows near solid boundaries was used to model the flow inside the porous region. Important results of engineering interest were obtained and are reported in this paper. These results thoroughly document the dependence of the Nusselt number on several parameters of the problem. Of particular importance is the finding that the dependence of Nu on the thickness of the porous layer is not monotonic. A critical thickness exists at which the value of Nu reaches a minimum.

Comparative Effects of Computer-Assisted Instruction: A Synthesis of Reviews:

Abstract: This article critically examines the literature reviews of computer-assisted instruction (CAI). Its purpose is to synthesize what is known about CAI at all levels of implementation. Sixteen reviews, three traditional and thirteen quantitative, are compared and evaluated. Results of the synthesis indicated that typical effect of CAI is to raise outcome measures moderately by 0.42 standard deviation units. Thus, the effect of CAI is to place the average student using it at the 66th percentile of the control group distribution.

On the effect of founder events on epistatic genetic variance.

Abstract: Mayr (1963) proposed that small isolated propagules from a large panmictic population would occasionally undergo a genetic revolution due to loss of genetic variability. More recently Templeton (1980a) has suggested that founder events may be much more important in systems that have strong epistasis. Because of the work of these and other authors it becomes an interesting theoretical problem to study the distribution of epistatic variance in a population following a founder event. In the model presented here measures of coancestry (Cockerham, 1967, 1984; Cockerham and Weir, 1973; Weir and Cockerham, 1973, 1977; Tachida and Cockerham, unpubl.) are used to examine the effect of founder events on additive-by-additive epistasis. Using this approach, the coancestries, or intraclass correlations, within individuals and within demes, together with the genetic variance components in the ancestral population are used to obtain the variance within and among demes following a founder event. Examples are analyzed for single founder events of 1-25 individuals and multiple founder events of two individuals. Following a single founder event, the contribution of the additive variance to the variance within demes relative to the additive variance in the ancestral population is always less than one. However, the contribution of epistatic variance to the variance within demes relative to the epistatic variance in the ancestral population is always greater than one. Thus, while a founder event decreases the contribution of additive variance to the variance within demes, it increases the contribution of epistatic variance to the variance within demes. The contribution of epistatic variance to the variance among demes following a single founder event is not qualitatively different from the contribution of additive variance to the variance among demes. These results indicate that epistatic variance is less likely than additive variance to cause a genetic revolution following a single founder event. When populations undergo multiple founder events the situation changes considerably. Epistatic variance may contribute as much as four times its original value to the variance among demes, while additive variance can contribute maximally twice its original value to the variance among demes. Thus, epistasis, which is relatively unimportant following a single founder event, may have major evolutionary implications if drift is allowed to continue for several generations.

Pathological supply dependence of O2 uptake during bacteremia in dogs.

Abstract: When systemic delivery of O2 [QO2 = cardiac output X arterial O2 content (CaO2)] is reduced, the systemic O2 extraction ratio [(CaO2-concentration of O2 in venous blood/CaO2] increases until a critical limit is reached below which O2 uptake (VO2) becomes limited by delivery. Many patients with adult respiratory distress syndrome exhibit supply dependence of VO2 even at high levels of QO2, which suggests that a peripheral O2 extraction defect may be present. Since many of these patients also suffer from serious bacterial infection, we tested the hypothesis that bacteremia might produce a similar defect in the ability of tissues to maintain VO2 independent of QO2, as QO2 reduced. The critical O2 delivery (QO2crit) and critical extraction ratio (ERcrit) were compared in a control group of dogs and a group receiving a continuous infusion of Pseudomonas aeruginosa (5 x 10(7) organisms/min). Dogs were anesthetized, paralyzed, and ventilated with room air. Systemic QO2 was reduced in stages by hemorrhage as hematocrit was maintained. At each stage, systemic VO2 and QO2 were measured, and the critical point was determined from a plot of VO2 vs. QO2. The mean QO2crit and ERcrit of the bacteremic group (11.4 +/- 2.2 ml.min-1.kg-1 and 0.51 +/- 0.09) were significantly different from control (7.4 +/- 1.2 and 0.71 +/- 0.10) (P less than 0.05). These results suggest that bacterial infection can reduce the ability of peripheral tissues to extract O2 from a limited supply, causing VO2 to become limited by O2 delivery at a stage when a smaller fraction of the delivered O2 has been extracted.(ABSTRACT TRUNCATED AT 250 WORDS)

Court-ordered obstetrical interventions

Abstract: In a national survey, we investigated the scope and circumstances of court-ordered obstetrical procedures in cases in which the women had refused therapy deemed necessary for the fetus. We also solicited the opinions of leading obstetricians regarding such cases. Court orders have been obtained for cesarean sections in 11 states, for hospital detentions in 2 states, and for intrauterine transfusions in 1 state. Among 21 cases in which court orders were sought, the orders were obtained in 86 percent; in 88 percent of those cases, the orders were received within six hours. Eighty-one percent of the women involved were black, Asian, or Hispanic, 44 percent were unmarried, and 24 percent did not speak English as their primary language. All the women were treated in a teaching-hospital clinic or were receiving public assistance. No important maternal morbidity or mortality was reported. Forty-six percent of the heads of fellowship programs in maternal-fetal medicine thought that women who refused medical advice and thereby endangered the life of the fetus should be detained. Forty-seven percent supported court orders for procedures such as intrauterine transfusions. We conclude from these data that court-ordered obstetrical procedures represent an important and growing problem that evokes sharply divided responses from faculty members in obstetrics. Such procedures are based on dubious legal grounds, and they may have far-reaching implications for obstetrical practice and maternal and infant health.