Breaking the language barrier: an emergentist coalition model for the origins of word learning

How do children learn their first words? The field of language development has been polarized by responses to this question. Explanations range from constraints/principles accounts that emphasize the importance of cognitive heuristics in language acquisition, to social-pragmatic accounts that highlight the role of parent-child interaction, to associationistic accounts that highlight the role of "dumb attentional mechanisms" in word learning. In this Monograph, an alternative to these accounts is presented: the emergentist coalition theory. A hybrid view of word learning, this theory characterizes lexical acquisition as the emergent product of multiple factors, including cognitive constraints, social-pragmatic factors, and global attentional mechanisms. The model makes three assumptions: (a) that children cull from multiple inputs available for word learning at any given time, (b) that these inputs are differentially weighted over development, and (c) that children develop emergent principles of word learning, which guide subsequent word acquisition. With few exceptions, competing accounts of the word learning process have examined children who are already veteran word learners. By focusing on the very beginnings of word learning at around 12 months of age, however, it is possible to see how social and cognitive factors are coordinated in the process of vocabulary development. After presenting a new method for investigating word learning, the development of reference is used as a test case of the theory. In 12 experiments, with children ranging in age from 12 to 25 months of age, data are described that support the emergentist coalition model. This fundamentally developmental theory posits that children construct principles of word learning. As children's word learning principles emerge and develop, the character of word learning changes over the course of the 2nd year of life.

Psychosocial job factors and return-to-work after compensated low back injury: a disability phase-specific analysis

BACKGROUND

Job characteristics may constitute a barrier to return-to-work (RTW) after compensated disabling low back pain (LBP). This study examines the impact of psychosocial job factors on time to RTW separately during the acute and subacute/chronic disability phases.

METHODS

This is a retrospective cohort study of 433 LBP workers' compensation claimants with 1-4 years of follow-up. The association of psychosocial job factors with duration of work disability was estimated with Cox regression models, adjusting for injury history and severity, physical workload, and demographic and employment factors.

RESULTS

High physical and psychological job demands and low supervisory support are each associated with about 20% lower RTW rates during all disability phases. High job control, especially control over work and rest periods, is associated with over 30% higher RTW rates, but only during the subacute/chronic disability phase starting 30 days after injury. Job satisfaction and coworker support are unrelated to time to RTW.

CONCLUSIONS

Duration of work disability is associated with psychosocial job factors independent of injury severity and physical workload. The impact of these risk factors changes significantly over the course of disability.

Estimating probability of non-response to treatment using mixture distributions

Repeat measurements of patient characteristics are often used to assess response to treatment. In this paper we discuss a normal mixture model for the observed change in the characteristic of interest in treated patients. The methods described can be used to estimate the overall proportion of non-response to treatment and also the probability that a patient has not responded to treatment given his or her observed change. The model parameters are estimated using maximum likelihood, and the delta method is used to construct a pointwise confidence band for the conditional probability that a patient is a non-responder to treatment. The work was initially motivated by analysis issues in the Fracture Intervention Trial (FIT), a randomized trial of the osteoporosis drug alendronate, and the method is illustrated with data from that study. We also evaluate key aspects of the estimation procedure with two simulation studies. In the first, the data generation model is the assumed normal mixture model, and in the second, the data are generated according to a shifted and scaled central t-distribution model suggested by the FIT data.

Development and validation of a prognostic index for 1-year mortality in older adults after hospitalization

CONTEXT

For many elderly patients, an acute medical illness requiring hospitalization is followed by a progressive decline, resulting in high rates of mortality in this population during the year following discharge. However, few prognostic indices have focused on predicting posthospital mortality in older adults.

OBJECTIVE

To develop and validate a prognostic index for 1 year mortality of older adults after hospital discharge using information readily available at discharge.

DESIGN

Data analyses derived from 2 prospective studies with 1-year of follow-up, conducted in 1993 through 1997.

SETTING AND PATIENTS

We developed the prognostic index in 1495 patients aged at least 70 years who were discharged from a general medical service at a tertiary care hospital (mean age, 81 years; 67% female) and validated it in 1427 patients discharged from a separate community teaching hospital (mean age, 79 years; 61% female).

MAIN OUTCOME MEASURE

Prediction of 1-year mortality using risk factors such as demographic characteristics, activities of daily living (ADL) dependency, comorbid conditions, length of hospital stay, and laboratory measurements.

RESULTS

In the derivation cohort, 6 independent risk factors for mortality were identified and weighted using logistic regression: male sex (1 point); number of dependent ADLs at discharge (1-4 ADLs, 2 points; all 5 ADLs, 5 points); congestive heart failure (2 points); cancer (solitary, 3 points; metastatic, 8 points); creatinine level higher than 3.0 mg/dL (265 micromol/L) (2 points); and low albumin level (3.0-3.4 g/dL, 1 point; <3.0 g/dL, 2 points). Several variables associated with 1-year mortality in bivariable analyses, such as age and dementia, were not independently associated with mortality after adjustment for functional status. We calculated risk scores for patients by adding the points of each independent risk factor present. In the derivation cohort, 1-year mortality was 13% in the lowest-risk group (0-1 point), 20% in the group with 2 or 3 points, 37% in the group with 4 to 6 points, and 68% in the highest-risk group (>6 points). In the validation cohort, 1-year mortality was 4% in the lowest-risk group, 19% in the group with 2 or 3 points, 34% in the group with 4 to 6 points, and 64% in the highest-risk group. The area under the receiver operating characteristic curve for the point system was 0.75 in the derivation cohort and 0.79 in the validation cohort.

CONCLUSIONS

Our prognostic index, which used 6 risk factors known at discharge and a simple additive point system to stratify medical patients 70 years or older according to 1-year mortality after hospitalization, had good discrimination and calibration and generalized well in an independent sample of patients at a different site. These characteristics suggest that our index may be useful for clinical care and risk adjustment.

Doctor proactive communication, return-to-work recommendation, and duration of disability after a workers' compensation low back injury

Although doctors are increasingly evaluated on the basis of return-to-work (RTW) outcomes, the effect of doctor-patient communication about the workplace and RTW after an occupational injury has received little research attention. The effect of patient-reported doctor communication on duration of disability was examined retrospectively in a 3-year cohort of 325 claimants with a lost-time low back injury. Although doctor proactive communication was associated with a greater likelihood of RTW during the acute phase (< 30 days of disability), this effect disappeared when injury and workload characteristics were taken into account. A positive RTW recommendation was associated with about a 60% higher RTW rate during the subacute/chronic phase (> 30 days of disability) only. Prospective studies are needed to confirm this effect. The impact of physician communication on RTW is largely confounded by injury and workplace factors.

Physical workplace factors and return to work after compensated low back injury: a disability phase-specific analysis

Little is known about predictors of duration of work disability (DOD). This cohort study of 433 workers' compensation claimants estimated DOD for job, injury, and demographic factors during consecutive disability phases using Cox regression analysis. DOD was calculated from administrative records. Results show that DOD increases with the time spent bending and lifting or pushing or pulling heavy objects at work, but it is unrelated to sitting, standing, or vibration. Younger age, longer pre-injury employment, less severe injuries, and a previous back injury predicted shorter disability, the latter factor only during the subacute/chronic disability phases. The effect of injury severity decayed over time. This study demonstrates the usefulness of a phase-specific analysis and shows that physical job and injury factors have a significant and time-varying impact on DOD.

A low pregnancy body mass index is a risk factor for an offspring with gastroschisis

A mother's prepregnancy obesity has been suggested as a risk factor for having offspring with an abdominal wall defect. We evaluated this hypothesis among 104 cases of gastroschisis--a severe birth defect of the abdominal wall most prevalent in infants of young women--and 220 controls with no defect. Using Quetelet's index (QI = weight in kg/height in m2) as a measure of body mass, we found a higher risk of gastroschisis (odds ratio (OR) = 3.2; 95% confidence interval (CI) = 1.4-7.3) for underweight mothers (QI<18.1 kg/m2) and a lower risk (OR = 0.2; 0.05-0.9) for overweight mothers (QI>28.3 kg/m2) as compared with mothers of normal weight. As QI was correlated to height, with the correlation varying according to mother's ethnicity and age, we adjusted for these factors in the analysis; the adjusted values approximated the unadjusted values. Evaluation of QI as a continuous variable showed that, for every unit increase in QI, the risk for gastroschisis decreased by about 11%. Sociodemographic, pregnancy, and nutrient factors did not confound the association. These results suggest that low prepregnancy body mass rather than obesity is a risk factor for gastroschisis.

Tear mixing under a soft contact lens: effects of lens diameter

PURPOSE

Tear exchange under a soft contact lens is modest, and higher exchange rates may be necessary to reduce extended-wear complications; what is not known is the optimal soft lens design to increase tear mixing. We explored the effect of lens diameter on tear mixing.

METHODS

Twenty-three subjects wore four different soft contact lenses with diameters of 12.0, 12.5, 13.0, and 13.5 mm. Tear mixing was quantified by placing fluorescein isothiocyanate-dextran on the posterior lens surface, inserting the lens, and monitoring the changes in fluorescence intensity in the postlens tear film. Tear mixing, expressed as the percentage decrease in fluorescence intensity per blink, was estimated using an exponential model. Lens movement was videotaped and lens comfort was graded on a 50-point scale (50 = excellent comfort). Subjects reporting a comfort level of less than 35 were excluded.

RESULTS

The mean +/- SE tear mixing rates were 1.82% +/- 0.17%, 1.61% +/- 0.16%, 1.34% +/- 0.17%, and 1.24% +/- 0.17% per blink for the 12.0-, 12.5-, 13.0-, and 13.5-mm diameter lenses, respectively. By regression analysis we found that, on average, mixing under the 12.0-mm lens was 0.59% per blink greater than with the 13.5-mm lens (P = .0024). Lens diameter was a significant predictor of lens comfort, and adjusting for the effects of comfort weakened the relationship between diameter and tear replenishment rate, although the mean rate under the 12.0-mm lens was still 0.43% per blink greater than with the 13.5-mm lens (P = .0468).

CONCLUSIONS

These data suggest that smaller-diameter soft lenses provide substantially better tear mixing than larger lenses; however, even small lenses provide modest tear mixing compared with rigid contact lenses.

Duration of work disability after low back injury: a comparison of administrative and self-reported outcomes

BACKGROUND

Workers' compensation wage replacement data have recently been used to estimate time to return to work (RTW) and the number of work days lost after occupational injury. The degree to which indemnity-based measures reflect self-reported work disability has until now not been studied.

METHOD

Kaplan-Meier curves of administrative and self-reported measures of duration of work disability were compared within a sample of 433 low back injury claimants followed up for 1 to 3.7 years.

RESULTS

Administrative measures consistently and significantly underestimated the duration of disability when compared to self-reported measures of RTW. The difference between the estimated mean number of work days lost for comparable administrative and self-reported measures ranged from 142 to 334 days.

CONCLUSIONS

Number of work days lost after low back injury is substantially underestimated by measures based on the duration of wage replacement benefits. This calls into question the adequacy of indemnity benefits and underscores the need for disability prevention programs.

Alternative approaches for measuring duration of work disability after low back injury based on administrative workers' compensation data

BACKGROUND

Studies of low back pain (LBP) disability remain largely incomparable because of different outcome definitions. To date, systematic comparisons of alternative outcome measures have not been made.

METHODS

Duration of work disability was studied in a 3-year cohort of 850 workers' compensation LBP claimants. Eleven administrative outcome measures were compared using Kaplan-Meier estimates of the proportion of claimants still on disability benefits during 3.5 years of follow-up.

RESULTS

The estimated mean duration of work disability was 75 days for the first temporary disability (TD) episode, 108 days for cumulative time on TD, and 337 for total compensated days, which includes all types of wage replacement benefits during vocational rehabilitation, temporary and permanent disability.

CONCLUSIONS

Commonly used administrative measures of lost workdays--time to first return to work and time on temporary disability--substantially underestimate the duration of work disability compared to measures based on all wage replacement benefits.

Intensive lifestyle changes for reversal of coronary heart disease

CONTEXT

The Lifestyle Heart Trial demonstrated that intensive lifestyle changes may lead to regression of coronary atherosclerosis after 1 year.

OBJECTIVES

To determine the feasibility of patients to sustain intensive lifestyle changes for a total of 5 years and the effects of these lifestyle changes (without lipid-lowering drugs) on coronary heart disease.

DESIGN

Randomized controlled trial conducted from 1986 to 1992 using a randomized invitational design.

PATIENTS

Forty-eight patients with moderate to severe coronary heart disease were randomized to an intensive lifestyle change group or to a usual-care control group, and 35 completed the 5-year follow-up quantitative coronary arteriography.

SETTING

Two tertiary care university medical centers.

INTERVENTION

Intensive lifestyle changes (10% fat whole foods vegetarian diet, aerobic exercise, stress management training, smoking cessation, group psychosocial support) for 5 years.

MAIN OUTCOME MEASURES

Adherence to intensive lifestyle changes, changes in coronary artery percent diameter stenosis, and cardiac events.

RESULTS

Experimental group patients (20 [71%] of 28 patients completed 5-year follow-up) made and maintained comprehensive lifestyle changes for 5 years, whereas control group patients (15 [75%] of 20 patients completed 5-year follow-up) made more moderate changes. In the experimental group, the average percent diameter stenosis at baseline decreased 1.75 absolute percentage points after 1 year (a 4.5% relative improvement) and by 3.1 absolute percentage points after 5 years (a 7.9% relative improvement). In contrast, the average percent diameter stenosis in the control group increased by 2.3 percentage points after 1 year (a 5.4% relative worsening) and by 11.8 percentage points after 5 years (a 27.7% relative worsening) (P=.001 between groups. Twenty-five cardiac events occurred in 28 experimental group patients vs 45 events in 20 control group patients during the 5-year follow-up (risk ratio for any event for the control group, 2.47 [95% confidence interval, 1.48-4.20]).

CONCLUSIONS

More regression of coronary atherosclerosis occurred after 5 years than after 1 year in the experimental group. In contrast, in the control group, coronary atherosclerosis continued to progress and more than twice as many cardiac events occurred.

Association between mothers' nutrient intake and their offspring's risk of gastroschisis

The young age of mothers of infants with gastroschisis, a congenital defect of the abdominal wall, suggested that deficient nutrition, with maternal-fetal competition for nutrients, could be a risk factor for gastroschisis. This population-based hypothesis-generating study consisted of 55 cases of gastroschisis and 182 matched controls. We assessed maternal nutrient intake during the trimester before conception with a self-reported food-frequency questionnaire and screened 38 nutrients to identify those most likely to be associated with gastroschisis. We used statistical classification trees to empirically generate cutpoints that determined the low and high levels of nutrient intakes corresponding to the risk of gastroschisis; cutpoints for most nutrients were similar to the corresponding recommended daily dietary allowances (RDAs). In univariate analysis, low intake of several nutrients emerged as the leading risk factors: carotenoids, e.g., alpha-carotene (odds ratio (OR) = 4.6; 95% confidence interval (CI) = 2.2-9.5), beta-carotene (OR = 3.1; 95% CI = 1.6-6.0); amino-acid compounds, e.g., total glutathione (OR = 3.5; 95% CI = 1.7-7.2); vitamin C (OR = 2.2; 95% CI = 1.5-7.8); vitamin E (OR = 2.3; 95% CI = 1.2-4.4); and minerals, fiber, and the fruit-and-vegetable group (OR = 3.1; 95% CI = 1.5-6.2). High intake of nitrosamines (OR = 2.4; 95% CI = 1.3-4.5) was also a good candidate. Many nutrient values were correlated and, in multivariate analysis, those most associated with gastroschisis were low alpha-carotene (OR = 4.3; 95% CI = 1.9-9.8), low total glutathione (OR = 3.3; 95% CI = 1.4-7.6), and high nitrosamines (OR = 2.6; 95% CI = 1.3-5.4). Adjusting for variables associated with gastroschisis in previous analyses of this population did not substantially alter those risks. These results suggest that maternal dietary inadequacy may be a risk factor for gastroschisis, and the three nutrients that emerged from the nutrient screening appear to be the best candidates to examine in further epidemiological analyses or biological studies.

Epithelial permeability reflects subclinical effects of contact lens wear

AIMS

Recently, it was reported by the authors that a single drop fluorophotometric technique for estimating corneal epithelial permeability (Pde) to fluorescein is not sufficiently precise for monitoring permeability changes in individual patients., but may be useful for evaluating mean differences in Pdc in population based research. To determine whether this technique provides a more sensitive index of epithelial integrity compared with conventional clinical assessments, the effects of mild corneal trauma on Pdc, the slit lamp appearance of the cornea, and corneal thickness (CT) were assessed.

METHODS

After baseline slit lamp examinations (SLE) and CT measurements, one randomly chosen eye of each of 32 normal subjects underwent 1 hour of closed eye soft contact lens (CL) wear while the fellow eye served as a control (no CL). After removing the CL, the SLE and CT measurements were repeated. Then, Pdc to fluorescein was assessed using a single drop fluorophotometric method refined to enhance feasibility, precision, and accuracy.

RESULTS

The mean (95% confidence interval) difference in natural log (Pdc) between 32 pairs of eyes (CL minus no CL) was 0.341 (0.069, 0.613), p = 0.016. By contrast, none of the 32 subjects exhibited corneal epithelial disruption upon SLE with white light following the closed eye period. Also, no substantial differences were apparent in the corneal swelling response between paired eyes, mean delta CT (95% CI) = -2.31(-7.53, 2.91) microns, p = 0.37.

CONCLUSIONS

Pdc measurements, used in studies of modest sample size, appear capable of detecting average differences in corneal barrier function that remain undetectable by SLE or pachymetry.

Corneal function during normal and high serum glucose levels in diabetes

PURPOSE

To assess corneal structure and the effects of acute hyperglycemia on corneal function in subjects with type 1 diabetes.

METHODS

Twenty-one diabetic and 21 nondiabetic volunteers of similar age were recruited. Baseline measurements of intraocular pressure (IOP), corneal thickness (CT), corneal autofluorescence (CAF), corneal sensitivity (CST), central and temporal endothelial cell density (DenC and DenT), and coefficient of variation in cell area (CVC and CVT) were taken. Corneal edema was induced, and the percent recovery per hour (PRPH) from hypoxic edema and endothelial permeability to fluorescein were determined. These procedures were done twice in the diabetic subjects under controlled euglycemic (EG) and hyperglycemic (HG) conditions, and once in control subjects while they were fasting.

RESULTS

Substantial differences in baseline measurements were found for IOP, CT, CAF, CST, DenC, and CVT. The mean +/- SE corneal swelling in the HG diabetic subjects (51.6 +/- 2.3 microm) was less when compared to the swelling in the EG diabetic subjects (56.2 +/- 1.87 microm, P = 0.05) and the control subjects (58.9 +/- 1.56 microm, P = 0.011). During euglycemia, the mean +/- SE PRPH was less in diabetic subjects than in control subjects (65.0 +/- 3.20 versus 73.8 +/- 1.81%/hour, P = 0.02) but did not differ in diabetic subjects under EG and HG conditions (65.0 +/- 3.20 versus 67.7 +/- 3.1%/hour, P = 0.56). No significant differences were noted between groups in endothelial permeability.

CONCLUSIONS

In addition to differences in baseline corneal structure, diabetic subjects showed less corneal swelling and reduced corneal recovery from hypoxia than did control subjects. During acute hyperglycemia, corneal swelling was less than during euglycemia in diabetic subjects, which suggests that hyperglycemia affected corneal hydration control.

Measurement of corneal epithelial permeability to fluorescein. A repeatability study

PURPOSE

Permeability (Pdc) to sodium fluorescein (F) is a characteristic of the barrier function of the corneal epithelium. The repeatability of several in vivo fluorophotometric methods used to measure permeability in humans remains largely undocumented. This study examines the repeatability of a method based on topical instillation of a single drop of F for the quantitative assessment of Pdc.

METHODS

Nine healthy subjects with no history of ocular disease provided 1 (n = 1), 2 (n = 1), or 3 (n = 7) repeated measurements of each eye at successive visits. After making 3 baseline fluorescence scans centrally through the tear film and cornea, 2 microliters of 0.35% F were instilled and 10 fluorescence scans were obtained at approximately 2-minute intervals immediately after instillation. Subsequently, the eyes were rinsed three times with nonpreserved saline and four additional scans were performed.

RESULTS

Pdc was calculated by dividing the baseline-corrected postrinse stromal fluorescence by the time integral of the tear film fluorescence calculated over the 20-minute exposure period. After applying a logarithmic transformation to the Pdc estimates, a mixed-model analysis was used to assess measurement repeatability. On the Pdc scale, there is an estimated 95% chance that a second measurement could be as much as 2.88 times higher or 0.35 times lower than a first measurement.

CONCLUSIONS

This substantial variability between repeated measurements indicates that the single-drop procedure is unreliable for monitoring individual patient changes. However, with careful sample size planning, this technique can be used in population-based research to compare differences in treatment effects between groups of subjects.

The association between pH level and corneal recovery from induced edema

Corneal acidosis has been shown to reduce corneal hydration control (CHC) as measured by the rate, expressed as the percent recovery per hour (PRPH), at which the thickness of the cornea decreases exponentially after an increased hydration load. Since the effect of pH on corneal function is of scientific interest and may have clinical implications, we explored the relationship between pH and PRPH in greater detail by examining the effect of different stromal pH levels on corneal hydration control. Corneal edema was induced using a 90-min exposure to wearing a hypoxic contact lens (CL). Following removal of the CL, random assignment over four eye-test combinations of either 0, 3, 5, and 7% CO2 were made while pH and corneal thickness were monitored using slit lamp fluorophometry and optical pachometry to measure corneal pH and corneal thickness, respectively. From these measurements we determined the pH-dose/PRPH relationship. The average stromal pH +/- 1SD resulting from exposure to either the 0, 3, 5, and 7% CO2, was 7.65 +/- 0.11, 7.30 +/- 0.09, 7.15 +/- 0.08 and 7.04 +/- 0.07 (p < 0.001), respectively. Analysis based on a quadratic model of the dose-response relationship between PRPH and corneal pH indicates that PRPH is relatively unchanged for pH in the physiological range (pH = 7.40-7.65) and then decreases notably below the physiological range.

Insulin resistance and insulin secretion are determinants of oral glucose tolerance in normal individuals

Plasma glucose values after oral glucose challenge vary widely in nondiabetic subjects. We have now evaluated the role of insulin resistance in determining the plasma glucose response to oral glucose in 74 volunteer subjects with normal glucose tolerance. In these subjects, we determined the plasma glucose and insulin responses over a 3-h period to a 75-g oral glucose challenge, and the steady-state plasma glucose concentration during a continuous infusion of somatostatin, glucose, and insulin (a quantitative measure of insulin resistance). The plasma glucose response was defined as the incremental increase in plasma glucose concentration above the fasting value for 3 h after the oral glucose challenge. Multiple regression analysis was used to define the relationship between the dependent variable (plasma glucose response) and various predictors of this response. These analyses indicated that both the steady-state plasma glucose and the incremental insulin response during the first 30 min after the glucose load were significant predictors of the plasma glucose response. In those individuals in whom insulin action was impaired and the 30-min plasma insulin response was decreased, plasma glucose values reached higher levels. When standardized regression coefficients were determined, the incremental glucose response was directly correlated with steady-state plasma glucose (r = 0.700, P < 0.001) and inversely with the insulin response during the first 30 min (r = 0.268, P = 0.023). Furthermore, the correlation between steady-state plasma glucose and glucose response was significantly greater (P < 0.005) than that between the glucose response and 30-min insulin concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Reduced postprandial cholecystokinin (CCK) secretion in patients with noninsulin-dependent diabetes mellitus: evidence for a role for CCK in regulating postprandial hyperglycemia

The plasma cholecystokinin (CCK) response to a test meal was studied in 16 control subjects and 15 patients with noninsulin-dependent diabetes mellitus (NIDDM). Basal CCK levels were approximately 1 pmol in both groups. However, after the test meal, plasma CCK levels were 2-fold greater in the controls when compared to the diabetics. In controls, CCK levels maximally increased by 5.6 +/- 0.8 pmol (mean +/- SEM) 10 min after feeding, whereas in the NIDDM patients this value was 1.9 +/- 0.6 pmol (P < 0.001). After the test meal, the normal subjects showed no postprandial rise in blood glucose, whereas the diabetic patient showed a rise of 2.6 +/- 0.7 mmol. To determine whether the decreased CCK levels may have been related to the postprandial hyperglycemia, 7 diabetic subjects were infused with CCK. With this CCK infusion, postprandial glucose levels did not rise. These data suggest, therefore: 1) a role for cholecystokinin in regulating postprandial hyperglycemia in man, 2) abnormalities in CCK secretion occur in NIDDM and may contribute to the hyperglycemia seen in this disease.

Cloning, sequencing, and expression in Escherichia coli of the coat protein gene of a new potyvirus infection South African Passiflora

Complementary DNA representing 1418 nucleotides (nt) of the 3'-poly(A)-proximal tract of the genomic RNA of a potyvirus causing woodiness disease in South African passion fruit, was cloned and sequenced. The sequence contained a single long open reading frame (ORF) of 1188 nt with no initiation codon, and a 3'-non-coding region (3'-NCR) of 230 nt followed by a poly-adenylate tract. Comparison of the ORF with other potyviral coat protein (CP) sequences led to the prediction that a 279 residue CP of MW 31722 is encoded by 836 nt at the 3'-terminus of the ORF. This virus is not merely a South African strain of passion fruit woodiness virus (PWV): the deduced CP sequence is only distantly related to CPs of other sequenced strains of PWV, although it is part of a distinct subgroup of potyviruses related to PWV. The virus was therefore designated as South African passiflora virus (SAPV). The DNA containing the putative CP was cloned into the pUEX2 bacterial expression vector and expressed in Escherichia coli as a beta-gal-CP fusion protein. The fusion protein reacted with polyclonal antisera raised against the native virus, and antisera raised against partially purified fusion protein reacted with viral CP in Western blots.

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.

Stromal acidosis affects corneal hydration control

An estimate of overall corneal hydration control can be obtained by measuring the rate of thickness recovery following induced corneal swelling; it is expressed as the percent recovery per hour (PRPH). This recovery is nearly, but not exactly, exponential, because there appears to be an initial slower recovery phase lasting about 30-40 minutes. This 30-40 minute period of slower recovery corresponds to the time when corneal pH is reduced secondary to the contact lens-induced swelling, suggesting the possibility that stromal acidosis may retard the corneal deswelling process. In this study, we explored the effects of corneal acidosis on hydration control by monitoring corneal recovery under normal and reduced pH conditions. Corneal pH was controlled by having subjects were goggles and exposing their eyes to air (normal pH) or a gas mixture providing 21% O2 and 7% CO2 (low pH). Relative corneal pH levels were monitored by measuring fluorescence intensity (FI) ratios, which showed that the average (+/- standard deviation) FI ratio was significantly lower under 7% CO2 (0.838 +/- .024) vs air (0.985 +/- .025; P = 0.0001), corresponding to approximate pH values of 7.25 vs 7.50. Under these reduced pH conditions, open-eye steady-state (OESS) corneal thickness was not substantially affected. For 10 subjects, mean (+/- SD) corneal thickness decreased 0.93 +/- 3.7 microns vs 1.10 +/- 4.50 microns after exposures to 60 minutes of 7% CO2 and 40 minutes of air (P greater than or equal to 0.45), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical assessment of corneal hydration control in Fuchs' dystrophy

The diagnosis and monitoring of Fuchs' disease is typically based on information obtained from patient symptoms and a slitlamp examination. Although this clinical information provides a basis for diagnosis, it does not give a quantitative method for charting the progression of the disease systematically or a reliable basis for predicting the cornea's capacity to remain transparent after stress (e.g., cataract extraction). However, it is possible to quantify overall corneal hydration control by inducing corneal swelling and then monitoring the deswelling rate expressed as percent recovery per hour (PRPH). We have tested subjects with Fuchs' dystrophy and found that the PRPH provides a reasonable estimate of corneal hydration control. Unfortunately, the PRPH procedure involves considerable time and technical assistance and therefore is not convenient for clinical practice. In this report, we document the results of an initial effort to explore the relations between PRPH and six clinical measures consisting of five biomicroscopic indices and a subjective synthesis of clinical information called the probability of decompensation (POD) based on these indices. PRPH was significantly related to striae (p less than 0.001), stromal haze (p = 0.025), microcysts (p less than 0.001), and the POD (p less than 0.001) and not significantly related to guttae (p = 0.252) or Descemet's folds (p = 0.185). An empirically weighted predictor of PRPH was constructed from a statistical analysis of five slitlamp assessments and age. This approach for synthesizing clinical information produced a result at least as good as that obtained from the POD summary. These results show an important link between a quantitative laboratory assessment of corneal function and a clinical evaluation of corneal status and suggest that with continued refinement, clinical assessment may provide more quantitative information on Fuch's dystrophy and other diseases that affect corneal status.

Ammonia assimilation and glutamate incorporation in coenzyme F420 derivatives of Methanosarcina barkeri

Methanosarcina barkeri was able to grow on L-alanine and L-glutamate as sole nitrogen sources. Cell yields were 0.5 g/l and 0.7 g/l (wet wt), respectively. The mechanism of ammonia assimilation in Methanosarcina barkeri strain MS was studied by analysis of enzyme activities. Activity levels of nitrogen-assimilating enzymes in extracts of cells grown on different nitrogen sources (ammonia, 0.05-100 mM; L-alanine, 10 mM; L-glutamate, 10 mM) were compared. Activities of glutamate dehydrogenase, glutamate synthase, glutamine synthetase, glutamate oxaloacetate transaminase and glutamate pyruvate transaminase could be measured in cells grown on these three nitrogen sources. Alanine dehydrogenase was not detected under the growth conditions used. None of the measured enzyme activities varied significantly in response to the NH4+ concentration. The length of the poly-gamma-glutamyl side chain of F420 derivatives turned out to be independent of the concentration of ammonia in the culture medium.

The molecular cloning and nucleotide sequencing of the 3'-terminal region of Ornithogalum mosaic virus

DNA complementary to the 3'-terminal 3684 nucleotides of the Ornithogalum mosaic potyvirus (OMV) genome was cloned and sequenced. The sequence consisted of a single large open reading frame which probably starts upstream of the cloned region. By comparison to other sequenced potyviruses, it was estimated that the clone contained the 3' non-coding (3'-NC) region, the coat protein (CP) gene and the large nuclear inclusion protein (NIb) gene, as well as approximately 85% of the small nuclear inclusion protein (NIa) gene. The 3'-NC region of 274 nucleotides showed 38% to 45% similarity to the corresponding regions of other potyviruses. The putative CP gene could encode a 253 amino acid coat protein with a calculated Mr of 28,807. Analysis of the amino acid sequences of OMV and other potyvirus proteins showed similarities of 66% to 77% for CP, 72% to 73% for NIb and 63% to 71% for NIa proteins. These data, as well as phylogenetic analysis of the CP sequences, suggested that OMV is a typical but taxonomically distinct potyvirus.

Hypoxic effects on corneal morphology and function

Normal corneal metabolism depends on a critical level of oxygen, below which a series of acute corneal responses occur, including an increase in stromal lactate, a reduction in intercellular pH, and an increase in corneal hydration. These acute responses are reversible when normal oxygen is restored; however, it has been shown that chronic exposure to low oxygen levels can result in permanent morphologic changes in the corneal endothelium. Clinicians have expressed concern that these observed structural changes may also be accompanied by alterations in corneal physiology. Whether such effects occur is not known, since it has been difficult to assess human corneal function accurately. Recently, we have developed an in vivo test, able to measure overall corneal hydration control, that can be used to study the effects of hypoxia on corneal function. This test provides information on several characteristics of hydration control, one of which is the percent corneal thickness recovery per hour (PRPH) after inducing corneal swelling. In this study, we assumed that corneal hypoxia accompanies both extended and polymethylmethacrylate (PMMA) contact lens wear and that the dose received is related to the years of past lens wear. Using this paradigm, we explored the relationship of hypoxic dose to an endothelial polymegethism index (EPI), endothelial cell density (ECD), and PRPH in 36 subjects with varying contact lens wearing histories. Based on multiple regression analysis, the relative change (expressed as percent per year) associated with hypoxic dose (adjusted for age and gender) was found to be dose-dependent and corresponded to estimated changes of 1.70%/yr, -0.25%/yr, and -1.26%/yr, with 95% confidence limits of (-0.3, 3.7), (-1.4, 0.9), and (-2.6, 0.06) for EPI, ECD, and PRPH, respectively. These preliminary data suggest that hypoxic exposure alters endothelial morphology and reduces corneal function; however, it is important to indicate that this was a exploratory investigation with several limitations, and that therefore these results should be viewed as preliminary until more definitive studies are completed.

Can lifestyle changes reverse coronary heart disease? The Lifestyle Heart Trial

In a prospective, randomised, controlled trial to determine whether comprehensive lifestyle changes affect coronary atherosclerosis after 1 year, 28 patients were assigned to an experimental group (low-fat vegetarian diet, stopping smoking, stress management training, and moderate exercise) and 20 to a usual-care control group. 195 coronary artery lesions were analysed by quantitative coronary angiography. The average percentage diameter stenosis regressed from 40.0 (SD 16.9)% to 37.8 (16.5)% in the experimental group yet progressed from 42.7 (15.5)% to 46.1 (18.5)% in the control group. When only lesions greater than 50% stenosed were analysed, the average percentage diameter stenosis regressed from 61.1 (8.8)% to 55.8 (11.0)% in the experimental group and progressed from 61.7 (9.5)% to 64.4 (16.3)% in the control group. Overall, 82% of experimental-group patients had an average change towards regression. Comprehensive lifestyle changes may be able to bring about regression of even severe coronary atherosclerosis after only 1 year, without use of lipid-lowering drugs.

Humidity effects on corneal hydration

Overall corneal hydration control expressed as the percent recovery per hour (PRPH) can be assessed with an exponential model that uses data derived from two kinds of corneal thickness measurements; one from monitoring recovery after inducing corneal swelling, and the other from measurements made after the eye has been open long enough to reach its open-eye steady-state (OESS) corneal thickness. Up to now these thickness measurements have been made without controlling the ambient humidity. It is possible that changes in relative humidity may effect tear film osmolarity sufficiently to change the state of corneal hydration. To evaluate the effects of humidity on hydration control, the OESS and PRPH were determined under several humidity levels. For both the OESS and the PRPH, two substudies were conducted. For the OESS, substudy 1 consisted of measuring corneal thickness when humidity was changed from 30% (ambient) to 52 or 97% controlled humidity. This resulted in mean +/- standard deviation (SD) changes in OESS thickness amounting to -0.33 +/- 3.5 microns and 2.6 +/- 3.4 microns, respectively, with a differential change of 2.94 +/- 3.04 microns (95% confidence interval [CI] from 0.77 to 5.11 microns). Corresponding results for substudy 2 connected with changes from 43% (ambient) to 12 or 97% controlled humidity were -2.4 +/- 2.7 microns and -0.3 +/- 1.9 microns, respectively, with a differential change of 2.1 +/- 1.8 microns (95% CI from 0.9 to 3.4 microns).(ABSTRACT TRUNCATED AT 250 WORDS)

Corneal hydration control in Fuchs' dystrophy

Corneal hydration control was tested in 22 patients with Fuchs' dystrophy, and eight subjects of similar age without the disease, by measuring the corneal thickness recovery from swelling induced by hypoxia or following overnight sleep. Measurement precision was enhanced by using a modified optical pachometer and conducting two test procedures which were analyzed by a coupled exponential model. We have identified three parameters of the recovery from corneal swelling which may be used to describe hydration control: percent recovery per hour (PRPH) (mean 25.4% for Fuchs' and 34.2% for normals), time for 95% of corneal thickness recovery (mean 10.2 hr for Fuchs' and 7.1 hr for normals), and the open-eye steady-state thickness (mean 562 microns for Fuchs' and 537 microns for normals.) A PRPH of 17.1%/hr was identified as the minimum below which the cornea could not regain its open-eye steady state during the entire day and approaches decompensation. Our test procedure quantifies the corneal hydration control mechanism and may provide a test of endothelial function which can be used to monitor the progression of Fuchs' disease and guide decisions related to corneal surgery.

Correlates of high density lipoprotein cholesterol in women studied by the method of co-twin control

This study examines the relation between each of the following risk variables and high density lipoprotein (HDL) cholesterol: cigarette smoking, alcohol use, leisure exercise, postmenopausal estrogen use, and body mass, before and after adjustment for genetic and nongenetic variables shared by monozygous and dizygous co-twins. Subjects were 179 dizygous and 255 monozygous twin pairs from the Kaiser Permanente Twin Registry who participated in a special examination in 1978-1979 in Oakland, California. A multivariate co-twin analysis made it possible to adjust for measured covariables and also to adjust for unmeasured familial variables shared by co-twins. After adjustment for measured covariables, further adjustment for the unmeasured familial variables shared by monozygous co-twins reduced a positive association between alcohol and HDL cholesterol and eliminated a positive association between exercise and HDL cholesterol. On the other hand, adjustment for unmeasured familial variables shared by monozygous co-twins had little effect on significant associations between smoking and HDL cholesterol, postmenopausal estrogen use and HDL cholesterol, and body mass and HDL cholesterol. Although an important role for random error was not ruled out in the sample size available, findings are consistent with the following interpretations: 1) alcohol consumption and leisure exercise may have smaller effects on HDL cholesterol than predicted by studies unadjusted for familial factors because effects of these variables are confounded by familial factors; and 2) smoking, postmenopausal estrogen, and body mass have effects predicted by studies unadjusted for familial factors and may therefore be good targets for interventions to raise HDL cholesterol.

Type A behavior pattern and health status after 22 years of follow-up in the Western Collaborative Group Study

Type A/B behavior has been studied extensively as a risk factor for coronary heart disease. This study tests the hypothesis that Type A/B behavior is associated with ill health in general. All-cause mortality was examined in the original cohort of 3,154 men aged 39-59 years at baseline in the Western Collaborative Group Study in 1960-1961. Morbidity was examined in a group of 2,365 men aged 61-81 years who were surviving members of the cohort in 1982-1983 and who agreed to fill out a self-administered health status questionnaire. On the basis of these data, a three-level general morbidity index was constructed that included coronary heart disease and a number of other chronic conditions. Type A/B behavior was not significantly associated with all-cause mortality over the 22-year follow-up. However, among men 61-71 years of age, behavior type assessed at the baseline examination 22 years earlier (1960-1961) was positively associated with the morbidity index (p less than 0.001). Furthermore, behavior type and the morbidity index showed a dose-response association; extreme Type A personalities had the highest level of morbidity, while those with the fewest Type A characteristics had the lowest level of morbidity. This general pattern of association was not due to the presence of coronary heart disease or to any other particular disease condition in the morbidity index and did not change when an ordinal logistic regression model was used to control for other baseline risk variables. For the older men (aged 72-81 years), the pattern of association was similar but did not reach statistical significance. Thus, in a group of men over 60, a positive association was found between general morbidity status and Type A/B behavior measured over two decades earlier.

Social connections and mortality from all causes and from cardiovascular disease: prospective evidence from eastern Finland

The association between an a priori measure of social connections and five-year mortality from all causes, cardiovascular diseases (International Classification of Diseases, Eighth Revision (ICD-8) codes 390-458), and ischemic heart disease (ICD-8 codes 410-414) was studied in 13,301 men and women from eastern Finland who were first interviewed in 1972 or 1977. For men, there was a graded association between extent of social connections and mortality. In multivariate models with adjustment for age, smoking, serum cholesterol, mean weighted blood pressure, measures of prevalent illness, and other possible confounders, men who were in the two lowest quintiles of the social connections scale were at increased risk compared with those in the highest quintile (odds ratio (OR)all cause = 1.54, 95% confidence interval (CI) = 1.21-1.95; ORcardiovascular disease = 1.54, 95% CI = 1.11-2.13; ORischemic heart disease = 1.34, 95% CI = 0.94-1.90). No strong or consistent association was found for women. The association for men was modified by levels of blood pressure with the effect of low social connections greater at higher levels of blood pressure. In three separate analyses, there was no evidence for confounding or effect modification due to prevalent illness at baseline.

Coronary heart disease mortality in the Western Collaborative Group Study. Follow-up experience of 22 years

In 1960-1961, 3,154 healthy, middle-aged men were entered into the Western Collaborative Group Study, a long-term study of coronary heart disease. A 22-year mortality follow-up of this cohort in 1982-1983 accounted for almost 99% of the cohort, and determined that 214 of the men had died of coronary heart disease. The risk of coronary heart disease mortality was studied for several variables measured at baseline, i.e., Type A/B behavior, systolic blood pressure, serum cholesterol level, cigarette smoking status, and age. Using a proportional hazards regression model, systolic blood pressure, serum cholesterol level, cigarette smoking status, and age were highly significant predictors (p less than 0.001) of 22-year coronary heart disease mortality. Type A/B behavior showed no association with 22-year coronary heart disease mortality (standardized relative hazard (SRH) = 0.98, 95% confidence interval (CI) = 0.85-1.12). Systolic blood pressure, serum cholesterol, and age showed relatively consistent positive associations with coronary heart disease mortality over four successive time intervals after the baseline examination. Cigarette smoking showed a significant positive association in the first and second intervals and a nonsignificant positive association in the third and fourth intervals. Type A/B behavior was positively but not significantly associated with coronary heart disease in the first and third intervals, significantly negatively associated (SRH = 0.70, 95% CI = 0.53-0.93) in the second interval and not associated in the fourth interval. The results confirm the importance of the traditional coronary heart disease risk factors, and raise a substantial question about the importance of Type A/B behavior as a risk factor for coronary heart disease mortality.

Type A behavior and mortality from coronary heart disease

The relation of behavior (Type A or Type B) to the morbidity and mortality of coronary heart disease (CHD) is still debated. We studied the survival of 257 male patients with CHD from the initial, 8.5-year phase of the Western Collaborative Group Study to see whether behavior type--as assessed by a structured interview before the CHD event--was related to subsequent CHD mortality. Behavior type was not related to mortality in 26 patients who died within 24 hours of the coronary event. However, of the 231 patients who survived for 24 hours, the mortality rate associated with CHD among 160 Type A patients studied during an average 12.7 years was 19.1 per 1000 person-years. This was unexpectedly lower than the corresponding rate of 31.7 among 71 Type B patients who were followed for an average of 11.5 years (P = 0.04). In a proportional-hazards survival analysis, which controlled for variable follow-up time, the type of initial coronary event, and traditional risk variables, the relative CHD-associated mortality rate among Type A as compared with Type B patients was 0.58 (P = 0.03; 95 percent confidence interval, 0.35 to 0.96). The lower mortality among Type A subjects occurred in both younger and older subgroups but was more pronounced in patients whose initial diagnosis was symptomatic myocardial infarction rather than silent myocardial infarction or angina pectoris. This apparent advantage associated with Type A behavior is surprising and needs confirmation, but the results do indicate that patients with CHD and a Type A behavior pattern are not at increased risk for subsequent CHD mortality.

Compliance to treatment for hypertension in elderly patients: the SHEP pilot study. Systolic Hypertension in the Elderly Program

Assessing the compliance of people over 60 years of age and older with an antihypertensive treatment regimen was a major objective of the Systolic Hypertension in the Elderly Program (SHEP) pilot study. The study randomized 551 men and women over the age of 60 (mean age = 72 years) to a stepped care treatment that included chlorthalidone or placebo in a double-blind trial. Three measures of compliance to treatment protocol--pill count, self-report, and a urine chlorthalidone assay--all indicated high levels of compliance in 80 to 90% of participants at 3 months and 1 year after randomization. Pill-taking compliance was similar in the active and placebo groups, although the rate of discontinuance from study medications at 1 year was higher in the placebo than in the active group. Compliance was high in all age categories, including those over age 80. These data suggest that elderly patients can achieve high levels of compliance with antihypertensive medications.

Type A behavior and cancer mortality. Theoretical considerations and preliminary data

If stress and cancer are related by coping failure, that connection presumably involves the immune system. This involvement has already been shown in animals. It can be hypothesized that Type A personalities (driving, impatient, sometimes hostile) go through states of repeated frustration because of unachieved goals. From that point of view, Type A individuals are alternately able to cope and unable to cope. Such a pattern would theoretically tend toward repeated episodes of suppression and recovery of the immune system, with increased probability of growth of transformed cells. An opposing hypothesis, derived from human survival studies, suggests that a subgroup of Type B individuals (termed "Type C"--accepting, giving-up) are more likely to suffer a poor prognosis. A preliminary study relating Type A/B behavior pattern to cancer mortality was done in a cohort of 3154 men from the Western Collaborative Group Study (WCGS). The cancer mortality rate for the period 1960-1977 was 0.037 for Type A subjects (58 cancer deaths/1589 Type A subjects), and 0.025 for Type B subjects, yielding an odds ratio of 1.55. The odds ratio dropped to 1.29 (95% confidence interval = 0.84-1.96) when controlled for age, cigarette smoking, serum cholesterol, systolic blood pressure, and education. Preliminary analysis from a follow-up to mid-1983 shows a similar association. The findings suggest that, if anything, Type A subjects are more likely to die of cancer than Type B subjects. Although the finding is not strongly suggestive of a clinically or theoretically significant association between Type A/B behavior pattern and cancer mortality, it is sufficiently interesting to warrant further investigation.

Corneal change accompanying orthokeratology. Plastic or elastic? Results of a randomized controlled clinical trial

Effects of orthokeratology on refractive error, visual acuity, and corneal curvature were monitored on two randomized comparison groups for 364 days of lens wear and 95 days of follow-up after lens wear was discontinued. Approximately 36% of the treatment group compared with 13% of the control group had 1 diopter or more change in refractive error; however, after lens wear was discontinued, there was substantial remission and differences between the groups were small. Although there was a positive correlation between the amount of change during lens wear and the persistence of change after discontinuation, neither the magnitude of persistence nor differences between groups were clinically important. The lack of persistence indicates that the cornea is either highly elastic or has some other memory mechanism. We conclude that orthokeratology produces modest reductions in myopia; however, the effect will not persist without continued lens wear and therefore is of limited clinical value in permanently reducing myopia.

Comparison of two therapeutic regimens using the same topical corticoid for stable psoriasis

In a masked, randomized, concurrently controlled clinical trial we compared the therapeutic response of two regimens in which the same topical corticoid was used to treat 52 men who had stable psoriasis. One regimen, called reduced dose, consisted of once-a-day application of a representative potent fluorinated topical steroid ointment, fluocinonide (Lidex), combined with three-times-a-day application of its vehicle. The other regimen, called traditional dose, consisted of four-times-a-day topical application of the same steroid. Patients were assigned to one of the two regimens and observed for six weeks. Confidence intervals for the difference in true mean response under these two regimens provide good evidence that for these patients the traditional dose was not clinically superior to the reduced dose.

The Berkeley Orthokeratology Study, part III: safety

The safety of orthokeratological (OK) procedures was assessed by monitoring several ocular characteristics including corneal thickness, refractive astigmatism, corneal astigmatism, correctable spectacle-acuity, corneal edema, corneal staining, and endothelial cell density. Safety was also assessed by reviewing the number and causes of extra clinical visits that occurred because of ocular complications and by determining whether safety factors were related to patients lost to follow-up. Over the 1.2-year period from the baseline examination to the end of the lens-wearing phase of the study, the Treatment (T) and Control (C) groups had, respectively, only small changes in their mean levels of corneal thickness (0.2 vs. 3.2 microns), refractive astigmatism (0.07 vs 0.01 D), and corrected spectacle acuity (0.02 vs 0.018 logarithm of the minimum angle of resolution). Analysis of time trend data obtained from scheduled monthly examinations also showed that changes in mean corneal thickness and mean corneal astigmatism were small and not clinically important in either comparison group during the course of the treatment. As a result of complications from lens wear, the T group required 1.25 times as many extra visits as the C group (p = 0.14). However, none of these visits provided sufficient clinical indication for the discontinuance of lens wear. Loss to follow-up typically occurred because of either poor compliance with the study protocol or loss of motivation caused by minor contact lens-related symptoms such as blurred vision, slight discomfort, or frequently lost lenses. These reasons were similar in both comparison groups. It appears that OK treatment is safe for the types of patients who participated in this study, but it may require more patient monitoring than would be needed to achieve and maintain a physiologically acceptable fit with conventional hard contact lens prescriptions.

The Berkeley Orthokeratology Study, Part I: General conduct of the study

The Berkeley Orthokeratology Study was a single center, randomized, concurrently controlled masked clinical trial. Eighty subjects were studied--40 in an orthokeratology (OK) treatment group and 40 in a control group fitted with conventional hard contact lenses. Visual and ocular characteristics were monitored for 1.5 years in order to assess relative efficacy, duration, and safety of the OK treatment. This report describes the general conduct of the study including recruitment methods, eligibility requirements, randomization and masking procedures, contact lens materials, and the treatment and follow-up plan. Baseline comparison revealed that the 21 subjects lost to follow-up were similar to the 59 subjects who completed follow-up and also that the 31 treatment and 28 control subjects in this group were quite similar in their baseline characteristics. In the course of adaptation and subsequent follow-up, treatment subjects were fitted with six lenses per eye on the average compared with three per eye in the control group. Analysis of lens prescriptions shows that the treatment lenses were substantially larger, thicker, and fitted optically flatter than those worn by the control group.

The Berkeley Orthokeratology Study, Part II: Efficacy and duration

Relative efficacy of orthokeratology (OK) was evaluated by assessing changes in refractive error, visual acuity, and corneal curvature in 31 treated and 28 randomized control subjects who wore conventional rigid contact lenses. The duration of changes was studied by monitoring subjects after lens wear was discontinued. After an average of 444 days of contact lens wear the treatment group showed an overall mean reduction in spherical equivalent refractive error of 1.01 D compared with 0.54 D in the control group (p = 0.02). Both groups had considerable variation in refractive error change. Corresponding mean improvements in unaided visual acuity were -0.27 and -0.20 log of the minimum angle of resolution [log (MAR)]. Corneal curvature decreased in both comparison groups, but the actual diopter value was about one-half that of the refractive change. The changes in these characteristics tended to occur during the first 132 days of wear, and additional aggressive lens therapy during the remaining 241 days of treatment produced little additional change. The refractive error fluctuated considerably during the period of follow-up and these fluctuations tended to be larger in those subjects who had shown greater changes in refractive error. When the lenses were removed, ocular characteristics returned steadily toward baseline levels. Ninety-five days after discontinuing lens wear, the refractive error had returned 75 and 69% of the way to baseline levels for the treatment and control groups, respectively. Visual acuity and corneal curvature showed similar rebound after 95 days. We conclude that it is possible to reduce myopia about 1D; however, the change is not permanent. Results indicate that the level of vision during periods of nonlens wear would be unstable, making it difficult to predict what the quality of vision would be under a retainer lens wear program.

A multivariate analysis of health-related practices: a nine-year mortality follow-up of the Alameda County Study

Associations between several common health-related practices and a variety of health outcomes have been reported. However, the independent associations between each of these practices and mortality from all causes have not been assessed. In the present report, a multiple logistic analysis of seven potentially health-related practices (individually and in a summary index) and mortality from all causes is conducted, using data from the Human Population Laboratory Study of a random sample of 6928 adults living in Alameda County, California in 1965 and a subsequent nine-year mortality follow-up. Many covariables such as physical health status and socioeconomic status are simultaneously analyzed. The health-related practices examined are: 1) never smoking; 2) regular physical activity; 3) low alcohol consumption; 4) average weight status; 5) sleeping seven to eight hours/night; 6) not skipping breakfast; and 7) not snacking between meals. The analysis reveals that five of the practices are associated with lower mortality from all causes. Neither eating breakfast nor not snacking have significant independent associations with lower mortality. After covariable adjustment, respondents who reported few low-risk practices have a relative risk of 2.3 (p less than 0.001) when compared with those who had many low-risk practices. Mortality risks for possible combinations of health-related practices are discussed.

Differentiating environmental from disease-related fevers in the term newborn

It is often difficult to differentiate environmental overheating from disease-related fever in the newborn. The purpose of this study was to establish the normal relationship between peripheral skin temperature and rectal temperature in normal newborn infants whose rectal temperatures were in the upper range of normal (99.0 to 99.6 F) and to compare it with that relationship in infants with fevers known to be disease related. Seventy-eight paired rectal and anterior mid-lower leg skin temperatures were obtained from 41 normal 2-day-old infants. Thirteen similar paired temperatures were measured in 13 full-term infants admitted from home with fever (greater than 100.0 F). The rectal temperature-leg temperature (RT-LT) difference in the normal infants ranged between -1 and +4 F, with a mean of +1.14 F, whereas in the febrile infants it ranged between +5.7 and 12.9 F with a mean of 7.90 F. In febrile infants there was no trend in RT-LT difference as rectal temperatures rose whereas normal infants showed a tendency toward a decreasing RT-LT difference with increasing temperatures. When an RT-LT difference of +3 F is chosen as an arbitrary boundary between environmentally overheated infants and infants with disease-related fevers, it is estimated that 0.5% of infants with disease-related fevers would be incorrectly classified. The RT-LT difference adds an objective guideline for evaluation of temperature elevation in the full-term, appropriate for gestational age neonate.

Contact lens effects on ametropia: a current example of the clinical trial

This paper describes the basic features of an ongoing double masked, randomized, controlled clinical trial which studies the changes in corneal and visual function that result when contact lenses are fitted in a manner designed to alter myopic refractive error. Subjects are randomly allocated to either a treatment or control group. Corneal and visual changes resulting from wearing lenses of these designs are compared to the effects of wearing contact lenses fitted in a standard clinical manner. Comparative analysis of the treatment and control groups is based on (1) visual acuity, (2) refractive error, (3) corneal thickness, (4) endothelial cell density, (5) external eye health, (6) corneal curvature, (7) duration of effect, and (8) predictive factors such as ocular rigidity and corneal topography. Essential parts of the experimental design and some results from the first phase of the study are reported.

Epidemiology as a guide to clinical decisions. The association between triglyceride and coronary heart disease

The hypothesis that triglyceride is a cause of coronary heart disease, although unconfirmed and never universally accepted, has nonetheless strongly influenced the practice of preventive medicine. We have examined the epidemiologic association between triglyceride and coronary heart disease to evaluate the validity of inferring that there is a causal relation between the two. Neither the evidence from published studies nor an analysis of data from the Western Collaborative Group Study provides strong support for the causal hypothesis. Information from other scientific disciplines is also meager, contrasting with the coherence of diverse evidence supporting the hypothesis that cholesterol is a cause of coronary heart disease. These arguments fall short of disproving the belief that lowering triglyceride will prevent coronary heart disease, especially since triglyceride and cholesterol are inextricably associated through mutual lipoprotein carriers. But we propose that the ethics of preventive medicine place the burden of proof on the proponents of intervention. We therefore recommend that widespread screening and treatment of healthy persons for hypertriglyceridemia be abandoned until more persuasive evidence becomes available.

Work activity and fatal heart attack studied by multiple logistic risk analysis

A group of 3975 San Francisco longshoremen in cohorts classified annually by work activity (WA) was followed for fatal heart attack (FHA) over a 22-year period. In 57,632 person-years of follow-up, 410 men died from heart attack. A multi-factor logistic analysis was used to study work energy output adjusted for age, race, systolic blood pressure, smoking, body mass index, glucose intolerance and EKG status as predictors of FHA. After adjustment for these factors, men with a high WA of 7 kcal/min above basal metabolism at the beginning of a yearly follow-up period had a FHA rate about one-half the rate for men in the lowest WA category of 1 kcal/min above basal metabolism (p = 0.0003). In addition, the predictability of average WA during the four years preceding a yearly follow-up period was isolated to see if the lower risk associated with high WA derives from selective factors. After adjustment for factors described above and also for rate of change in WA used to represent selective factors, subjects with WA of 7 kcal/min still had about one-half the FHA rate observed for men at the lowest WA level (p = 0.0006). The findings from these and other phases of the analysis are consistent with the hypothesis that a substantial protective effect against FHA results from vigorous physical exertion.