Spatial orientation by Salamanders using plane-polarized light.

Tiger salamanders (Ambystoma tigrinum) can perceive the plane of polarization in linearly polarized light and can learn to use that e-vector direction for spatial orientation in indoor orientation tests.

Extraoptic celestial orientation in the southern cricket frog Acris gryllus.

Celestial orientation and setting of the biological clock in the southern cricket frog Acris gryllus can be cued by light stimuli received by extraoptic receptors in the brain. These extraoptic photoreceptors may also be used in learning new orientational directions. A mechanism for a light-activated biological clock is discussed.

How much do persons with Alzheimer's disease cost Medicare?

BACKGROUND: Medicare claims are increasingly being used to identify persons with chronic diseases such as Alzheimer's disease (AD) for the purpose of determining the cost to Medicare of caring for such persons. Past work has been limited by the use of only 1 or 2 years of claims data to identify cases, leading to worries that this might lead to an undercount of prevalent cases and bias cost findings. OBJECTIVES: To analyze the average total cost to the Medicare program in 1994 of persons with a claims-based diagnosis of AD, using a 12-year period of claims history to identify prevalent cases, and to investigate the effect on cost of time since diagnosis. DESIGN: A cross-sectional design with a 12-year retrospective period to identify persons with AD. SETTING: Medical care practices, hospitals, and other providers of services to Medicare beneficiaries in the US in 1994. SUBJECTS: Respondents to the screener (n = 10,858) and community (5429) and institutional (n = 1341) questionnaire of the 1994 National Long Term Care Survey, with and without a claims-based diagnosis of AD. MEASUREMENTS: Average total cost to Medicare in 1994, measured as the actual amount Medicare paid for inpatient, outpatient, home health, skilled nursing facility, hospice, and Part B services, including payments to physicians, and other items such as durable medical equipment. We also measured disability in a variety of ways, including cognition, activity limitations, and residence in a nursing home. RESULTS: The average total cost to Medicare of persons with a claims-based diagnosis of AD was $6021 versus $2310 (P < .001) for persons without a diagnosis. When adjusting for patient characteristics, the ratio of cost between persons with AD and those without was reduced to about 1.6 to 1. Time since diagnosis was an important predictor of average total cost in 1994, with each additional year since diagnosis resulting in a $248 (P = .04) decrease in total cost (about 10% of the total sample mean cost of $2426). There was mixed evidence that persons with a diagnosis of AD incurred less cost than otherwise similarly disabled Medicare beneficiaries. CONCLUSIONS: Time since diagnosis with AD is an important predictor of cost and one that should be explicitly included in any rate-setting formula. Expanding the period used to identify cases resulted in an increase in the unadjusted ratio of cost of a Medicare beneficiary with AD relative to one without primarily because our control group costs are lower compared with those of past work.

The effect of middle- and old-age body mass index on short-term mortality in older people.

OBJECTIVES: To determine the effect of body mass index (BMI) at old age and at age 50 on short-term survival among persons age 65 and older. DESIGN: Cross-sectional, using the 4,791 respondents to the community interview of the 1994 National Long Term Care Survey (NLTCS). SETTING: United States of America. PARTICIPANTS: Persons age 65 and older who lived in community settings as of the 1994 NLTCS interview. MEASUREMENTS: Short-term mortality was measured from the date of the 1994 NLTCS through year-end 1995. BMI (kg/m2) (at three points: 1994 NLTCS, 1 year before, age 50) and all other variables, including three other modifiable risk factors known to be related to mortality--cigarette smoking, alcohol consumption, and exercise--were based on self-report. RESULTS: Both the unadjusted and adjusted nadirs of mortality in relation to BMI at old age were found in older persons with a BMI between 30 and 34.9; this was true for males and females in all age groups. The highest mortality rates were found for older persons with very low BMI (<18.5). In contrast, BMI at age 50 was positively related to mortality, with those in the lowest BMI category (<18.5) at age 50 having the lowest mortality. Persons who were obese at age 50 and who were no longer obese at the 1994 NLTCS had lower mortality than persons with stable weight. CONCLUSIONS: Weight reduction by middle-aged persons who are obese should be reinforced as a public health priority, because there is evidence that long-term weight loss results in better short-term survival. Further study of healthy older survivors to determine why they are not harmed by heavier weight in old age may provide useful insights into successful aging.

Circadian modulation of the rat acoustic startle response.

The acoustic startle response (ASR) of male rats was measured during several sessions over a 24-hr period in both a light-dark cycle and a constant-dark condition. Each session consisted of 10 trials each at 80, 90, 100, 110, and 120 dB white noise. The results indicate robust daily and circadian modulation of ASR amplitude that consist of an approximately twofold nocturnal increase at eliciting-stimuli intensities above 80 dB. Similar results were observed in female rats in constant-dark conditions. To determine whether daily changes in auditory thresholds were responsible for the observed modulation, ASR reflex modification procedures were used. These procedures were designed to measure auditory thresholds at frequencies of 10 and 40 kHz at several times of day. The results suggest a lack of significant circadian differences in auditory thresholds at these frequencies. This study demonstrates a novel role of the rat circadian system in the modulation of ASR amplitude.

Measurement of the electrokinetic properties of vaccinia and reovirus by laser-illuminated whole-particle microelectrophoresis.

The electrokinetics of vaccinia virus and reovirus type 3 were studied in dilute electrolyte solutions by whole-particle microelectrophoresis with dark-field laser illumination. The electrophoretic mobilities were dependent upon pH and electrolyte composition. The isoelectric point of vaccinia virus in dilute NaCl was 4.8 +/- 0.1; that of reovirus was 3.8 +/- 0.1. The mobility of reovirus was -2.65 +/- 0.30 micrometer . S-1 . V-1 . cm-1. Treatments known to cause irreversible changes in the structure of vaccinia, such as heating to 90 degrees C or exposure to pH 10, altered the virus's mobility under the reference conditions. The practical range of whole-particle microelectrophoresis thus extends to microorganisms as small as reovirus, allowing their electrokinetic and related surface properties to be studied.

Maternal exposure to 1,1,2-trichloroethylene affects myelin in the hippocampal formation of the developing rat.

The effect of 1,1,2-trichloroethylene (TCE), an industrial solvent, on myelin in the dorsal hippocampus of the developing rat was investigated. Rat pups were exposed to TCE via their dams' drinking water while in utero and until they were sacrificed at 21 days of age. Frozen coronal sections through the dorsal hippocampus were stained for the presence of myelin using a modification of the Heidenhain procedure developed for frozen sections. A significant decrease in myelinated fibers was found in the stratum lacunosum-moleculare, an area comprised of distal dendritic profiles of CA1 pyramidal neurons which receive input from the entorhinal cortex. These findings suggest that the reduction in myelin in the hippocampus may be responsible, in part, for behavioral effects observed following TCE exposure.

In vitro culture of Echinococcus multilocularis: protoscolicidal action of praziquantel and albendazole sulphoxide.

The metacestode stage of Echinococcus multilocularis was cultured in vitro. Sensitivity of protoscoleces to the presence of albendazole sulphoxide, praziquantel and methanol was assessed. 10 micrograms/litre of praziquantel or 500 micrograms/litre of albendazole sulphoxide significantly reduced protoscolex viability. The presence of methanol (at 0.25%) had no significant effect. In vitro culture of E. multilocularis can be used to assess possible chemotherapeutic agents.

Echinococcus multilocularis: in vivo results of therapy with albendazole and praziquantel.

The effects of albendazole and praziquantel on the growth of Echinococcus multilocularis were studied in cotton rats. Albendazole (20 and 50 mg/kg) reduced parasite weight and increased the length of survival of infected animals but viable infection was present after treatment. In an in vitro system albendazole sulphoxide entered cysts of E. multilocularis passively. Praziquantel 100 mg/kg was ineffective but 500 mg/kg significantly inhibited growth. A combination of albendazole and praziquantel was no more effective than either agent alone.

Combination chemotherapy of Echinococcus granulosus--in vitro studies.

Both benzimidazole carbamates and isoquinoline compounds have activity against protoscoleces of Echinococcus granulosus in culture in vitro; combinations of albendazole sulphoxide and praziquantel are more effective than either agent alone.

Echinococcus granulosus: in vitro maintenance of whole cysts and the assessment of the effects of albendazole sulphoxide and praziquantel on the germinal layer.

Small entire cysts of Echinococcus granulosus of human and animal origin were cultured in vitro in the presence or absence of albendazole sulphoxide (1000 micrograms/litre) or praziquantel (500 micrograms/litre) for 10 or 11 d, and subsequently passaged into the peritoneal cavity of gerbils to assess viability by continued cyst growth. Viability was reduced in the presence of albendazole sulphoxide, and disintegration of the germinal layer immediately after culture was demonstrated at the ultrastructural level. Praziquantel had no apparent effect on cyst growth.

Hospital ownership and cost and quality of care: is there a dime's worth of difference?

Nonprofit organizations may predominate when output quality is difficult to monitor. Hospital care has this characteristic. This study compared program cost and quality of care for Medicare patients hospitalized following onset of four common conditions by hospital ownership. Payments on behalf of Medicare patients admitted to for-profit hospitals during the first 6 months following a health shock were higher than for those admitted to other hospitals. With quality measured in terms of survival, changes in functional and cognitive status, and living arrangements, we found no differences in outcomes by hospital ownership.

Effect of Tween 80 on exploratory behavior and locomotor activity in rats.

Exploratory behavior and locomotor activity is enhanced in male rat pups (aged 10 to 20 days) whose dams received a chronic dose (1.25 ml/l) of Tween 80 via their drinking water. This enhancement manifests itself during the diurnal period of the day. These data suggest that Tween 80 has an effect on the CNS which could lead to misinterpretation of results in toxicology studies that use this compound as a dosage vehicle.

2-Deoxyglucose uptake in the developing rat brain upon pre- and postnatal exposure to trichloroethylene.

Trichloroethylene (TCE) is a widespread contaminant of drinking water sources. The effects of TCE on 2-deoxyglucose uptake by brain tissue were examined in pups from rat dams exposed to TCE in their drinking water. The pups were exposed throughout gestation and lactation. Deoxyglucose uptake in the cerebellum, hippocampus and whole brain of the pups during the first 21 days of life was measured using a modification of the 2-deoxy-D-glucose (2-DG) technique. We determined that TCE at a nominal concentration of 312 mg/l significantly depressed 2-DG uptake in the whole brains and cerebella of 7- to 21-day old pups. 2-DG uptake was also lower in the hippocampus of exposed pups at 7, 11 and 16 days, but returned to control levels by 21 days. No overt toxicity, such as lower body or brain weight, was observed at this exposure level. This decrease in 2-DG uptake reflects a decrease in glucose uptake and/or metabolism in the brains of animals exposed to TCE.

The effects of lead on the developing central nervous system of the rat.

Biochemical and structural development of the cerebral cortex of rat pups is delayed by low levels of lead administered in the dam's drinking water during gestation and suckling periods. These changes in brain development coincide with delays in the development of exploratory and locomotor activity and impaired learning. Subsequent cross-fostering experiments have shown that delays in synaptogenesis and in the development of exploratory behavior were attributed entirely to the prenatal, as opposed to the postnatal, exposure to lead at the low dose levels utilized. Examination of the variations in blood lead concentrations in pups and dams during gestation and until weaning at 21 days of postnatal age indicated that a substantial increase in blood lead concentrations occurred late in pregnancy. At 200 mg of Pb/liter of drinking water, peak blood Pb concentrations were observed to be approximately 60 micrograms/dl in dams and 80 micrograms/dl in pups on the 20th day of gestation. By the 10th postnatal day blood Pb concentrations had decreased to 35 micrograms/dl in dams and 40 microgram/dl in pups despite an increased consumption of drinking water containing the same concentration of Pb during this period. (Delays in cerebral cortical development were observed after 10 days of postnatal age). Tracer studies utilizing 203Pb indicate that the rate of Pb absorption was substantially increased in the pregnant, relative to the non-pregnant, dam. Although a similar increase in 45Ca absorption was also observed during pregnancy, increases in Pb absorption were enhanced by Pb-pretreatment, whereas Ca absorption was independent of Pb-pretreatment. From this data it is concluded that the apparently greater sensitivity of postnatal development on prenatal Pb exposure is secondary to enhanced Pb absorption in the pregnant rat. In vitro metabolic studies in isolated cerebral cortex slices taken from 15 day old rat pups exposed to Pb revealed increased glucose and oxygen consumption in response to elevations in the potassium concentration of the incubation media. This evidence of metabolic uncoupling in the immature rat cerebral cortex may be causally related to the measured delays in brain development.

Daily rhythmicity of the rat acoustic startle response.

We have measured the acoustic startle response (ASR) amplitude and latency in rats housed in a 12:12 light:dark (LD) cycle. The response amplitudes to eliciting stimuli (ES) of 110 dB or 120 dB (white noise) were significantly higher (nearly two-fold) during D than during L. Similar, but nonsignificant, trends were also observed at ES intensities of 90 dB or 100 dB. While some significant LD ASR latency differences were observed, we cannot ascribe them to the photoperiodic phase at this time. These findings conclusively demonstrate that the mammalian ASR amplitude exhibits daily rhythmicity.

The natural life of policy indices: geographical problem areas in the U.S. and U.K.

In spite of many fundamental differences between the health systems in the U.S. and U.K., each has pursued a policy of identifying geographical small-areas believed to have inadequate primary care physicians given local health care needs. The magnitude of the problems in such areas differ in the U.S. and U.K. leading to idiosyncratic policy responses that are dictated by overall health system realities. However, there are several common themes identified in this comparative study: goals for remedial health policy are often unclear, making evaluation difficult; in the absence of conceptual clarity, a consensus-based approach of identifying existing and widely available variables to designate areas has been used to identify geographical problem areas; there are widespread concerns that the present indices used to implement policy are inappropriate, but no alternative index has been adopted. The paper concludes that clarifying goals for remedial health policy is key if the effectiveness of such policy is to be improved. Guidelines for assessing the usefulness of existing and future indices used to designate areas as eligible for resources as a part of this type of small-area remedial policy are developed from this U.S./U.K. comparison.

Lead inhibits acquisition and retention learning in bullfrog tadpoles.

Bullfrog, Rana catesbeiana, tadpoles were exposed to 0, 500, 625, 750 or 100 micrograms Pb/L as lead nitrate, and subjected to learning and retention tests. Tadpoles used in learning acquisition tests were exposed for six days (144 hours) and tadpoles used in retention tests were exposed for five days (120 hours). All tadpoles were conditioned, using shock avoidance, to associate illumination (conditioned stimulus) with shock (unconditioned stimulus). The mean latency to respond, the number of avoidances, and the differences in learning curves of the lead-exposed and control tadpoles were compared statistically. Learning acquisition tests showed increased latencies and fewer avoidances in lead-exposed as compared to control tadpoles. Retention tests showed increased latencies and fewer avoidances in tadpoles exposed to 625, 750 and 1000 micrograms Pb/L as compared to controls.

Developmental neurotoxicity following premating maternal exposure to hexachlorobenzene in rats.

The maternal transfer of hexachlorobenzene (HCB) may place the developing organism at risk. The present study assessed the developmental neurotoxicity of HCB using a battery of behavioral tests. Two weeks prior to breeding, maternal rats were exposed via gavage to either 10 or 100 mg HCB/kg body weight. Behaviors evaluated in pups exposed maternally to HCB included the negative geotaxic reflex on postnatal day (PND) 6, 8, and 10, olfactory discrimination (PND 9-11), and the development of exploratory behavior (PND 15-20). Significant effects in these three tests indicated hyperactivity in HCB-exposed pups. No significant effects on learning (swim T-maze) or motor activity were detected in older offspring (PND 40 and 50 respectively). The acoustic startle response (ASR) revealed apparent age-related effects of maternal HCB exposure. On PND 23 pups from the high treatment group demonstrated significantly reduced ASR amplitude, whereas these same animals, tested on PND 90 (using a reflex modification design), showed elevated ASR amplitude relative to the controls. This work demonstrates that HCB is a behavioral teratogen, and suggests that human fetuses and suckling infants may be at risk from the neurotoxic effects of HCB.

General practitioner turnover and migration in England 1990-94.

BACKGROUND: In tandem with fears about a GP workforce crisis, increasing attention is being focused on the supply and distribution of primary care services: on general practitioners in particular. Differential turnover and migration across health authority boundaries could lead to a maldistribution of GPs, yet comprehensive studies of GP turnover are non-existent. AIM: To quantify general practitioner (GP) turnover and migration in England from 1990 to 1994. METHOD: Yearly data from 1 October 1990 to 1 October 1994 were collected on GPs in England practising full time, including average yearly turnover, rates of entry to and exit from general practice, and net migration among GPs. All were calculated at the family health service authority (now the new health authorities) level. RESULTS: Average yearly GP turnover ranges from 2.9% in Shropshire to 7.8% in Kensington, Chelsea and Westminster; turnover is associated with deprivation and high-need areas. Migration of GPs across health authority borders was rare. Entry and exit rates were also positively related to measures of deprivation and need. Relatively underprovided health authorities lost 23 GPs over the study period as a result of migration; relatively overprovided ones gained three. CONCLUSION: Turnover is driven primarily by exits from general practice and is related to deprivation and high need. Retention appears to be the main problem in ensuring an adequate GP supply in relatively deprived and underprovided health authorities.