Biomedical subjects

M Packard

Publications and source records attributed to M Packard.

7 recordsLinked to original sources

PubMed2000

Visual function and brain organization in non-decussating retinal-fugal fibre syndrome.

Functional neuroimaging, psychophysical and electrophysiological investigations were performed in a patient with non-decussating retinal-fugal fibre syndrome, an inborn achiasmatic state in which the retinal projections of each eye map entirely to the ipsilateral primary visual cortex. Functional magnetic resonance imaging (fMRI) studies showed that for monocularly presented simple visual stimuli, only the ipsilateral striate cortex was activated. Within each hemisphere's striate cortex, the representation of the two hemifields overlapped extensively. Despite this gross miswiring, visual functions that require precise geometrical information (such as vernier acuity) were normal, and there was no evidence for the confounding of visual information between the overlapping ipsi-lateral and contralateral representations. Contrast sensitivity and velocity judgments were abnormal, but their dependence on the orientation and velocity of the targets suggests that this deficit was due to ocular instabilities, rather than the miswiring per se. There were no asymmetries in performance observed in visual search, visual naming or illusory contour perception. fMRI analysis of the latter two tasks under monocular viewing conditions indicated extensive bilateral activation of striate and prestriate areas. Thus, the remarkably normal visual behavior achieved by this patient is a result of both the plasticity of visual pathways, and efficient transfer of information between the hemispheres.

Adolescent↗

PubMed1999

The Drosophila beta-amyloid precursor protein homolog promotes synapse differentiation at the neuromuscular junction.

Although abnormal processing of beta-amyloid precursor protein (APP) has been implicated in the pathogenic cascade leading to Alzheimer's disease, the normal function of this protein is poorly understood. To gain insight into APP function, we used a molecular-genetic approach to manipulate the structure and levels of the Drosophila APP homolog APPL. Wild-type and mutant forms of APPL were expressed in motoneurons to determine the effect of APPL at the neuromuscular junction (NMJ). We show that APPL was transported to motor axons and that its overexpression caused a dramatic increase in synaptic bouton number and changes in synapse structure. In an Appl null mutant, a decrease in the number of boutons was found. Examination of NMJs in larvae overexpressing APPL revealed that the extra boutons had normal synaptic components and thus were likely to form functional synaptic contacts. Deletion analysis demonstrated that APPL sequences responsible for synaptic alteration reside in the cytoplasmic domain, at the internalization sequence GYENPTY and a putative G(o)-protein binding site. To determine the likely mechanisms underlying APPL-dependent synapse formation, hyperexcitable mutants, which also alter synaptic growth at the NMJ, were examined. These mutants with elevated neuronal activity changed the distribution of APPL at synapses and partially suppressed APPL-dependent synapse formation. We propose a model by which APPL, in conjunction with activity-dependent mechanisms, regulates synaptic structure and number.

Amino Acid Sequence↗

PubMed1995

Inheritance of histiocytosis in Bernese mountain dogs.

One hundred and twenty-seven cases of histiocytosis in Bernese mountain dogs (BMD) were evaluated to determine if the tumour is inherited. Family data ruled out autosomal recessive, autosomal dominant and sex-linked modes of inheritance. The trait was determined to be inherited with a polygenic mode of inheritance. The salient points permitting this conclusion are: pedigrees developed from independently selected propositi link up allowing the tracing of all cases through several generations; multiple cases occur in the same litter; multiple cases have been produced by given dams and sires; there is a higher frequency of the disease among offspring of affected parents when compared to offspring of normal parents that produced histiocytosis and all offspring in the general population of BMDs; the fact that histiocytosis is common in BMDs and rare in eight other breeds and accounts for 25.4 per cent of the 500 tumours studied in this breed. The heritability of this trait was calculated to be 0.298.

Animals↗

PubMed1985

Health status of new retired-worker beneficiaries: findings from the New Beneficiary Survey.

In general, individuals who first received social security retired-worker benefits in June 1980-May 1981 viewed themselves as being in good health. They reported this view in response to questions in the 1982 New Beneficiary Survey conducted by the Social Security Administration. Two-thirds of the respondents in the retired-worker sample reported having no health-related work limitations and no moderate or severe functional activity limitations. However, more than half of those who did report such limitations indicated that the limitations were severe enough to keep them from any work for pay. Beneficiaries whose first monthly benefits were claimed at age 62 were more likely to report themselves in poor health than those receiving a first benefit at age 63 or older, but even among the 62-year-olds, more than three-fifths reported no work-limiting conditions.

Age Factors↗

PubMed1983

Slowing down pension indexing: the foreign experience.

Between 1975 and 1983, Canada, Finland, Sweden, the United Kingdom, and the Federal Republic of Germany--countries faced with immediate or long-term financing difficulties in their social security systems--modified their social security pension adjustment procedures. These changes in pension adjustments very often were made in conjunction with other restrictive measures such as increased contribution rates and/or contribution ceilings, or tightened criteria for eligibility of benefits. Four types of changes, applied separately or in combination, were made to slow down the rate of pension growth: (1) changing to a different index or modifying the index in use (Finland, Sweden, and the United Kingdom); (2) delaying implementation of pension adjustments (Finland and Sweden); (3) capping annual pension increases (Canada and West Germany); and (4) changing the index review period (the United Kingdom). Generally, these changes have had the desired effect of reducing pension growth. Finland, however, changed its indexing procedure in 1977 only to find that the new index grew faster than the old index for both 1978 and 1979. Since 1980, however, Finland's new pension adjustment index has been growing less rapidly than its old index.

Canada↗

PubMed1982

Mortality and early retirement.

This article examines and compares the survival rates of persons claiming retired-worker benefits at age 62 with those who did not. The study is based on a sample of Social Security insured workers who reached age 62 during the period 1962-72. The proportion of men dying in the initial years after age 62 was higher among those who claimed benefits at age 62 than among those who did not. The same pattern held for women but the difference was very small. To the extent that survival after age 62 can be taken as an indication of health status at age 62, these data suggest that the age-62 claimants were somewhat more likely than others to have had health problems. The difference in survival rates between the two groups, however, was not as great as the difference in the incidence of health problems reported in surveys. Past surveys have shown that men receiving early retirement benefits were twice as likely as other men to report health problems. According to this study, survival rates for men claiming benefits at age 62 were only 3-5 percentage points lower by age 68 than those for other insured men. Within any given age cohort, the difference between survival rates of age-62 claimants and other insured men widened over time. Survival rates improved across the age cohorts. Among the men, survival rates improved somewhat more for the age-62 claimants than for others.

Age Factors↗

PubMedDate not supplied

Seeing to one's self. Those who care for persons with AIDS must also preserve their own well-being.

Those who care for persons with AIDS face a number of special issues. They must understand the complex clinical course of the disease, be ready to cope with its devastating effects on patients, know how to address social prejudices against persons with AIDS, and be prepared to deal with the stresses of providing care under difficult circumstances. To be effective, care givers must know how to take care of themselves. Having a philosophy of care is one key component of self-care because it gives care givers a clear sense of direction and helps them enjoy a greater sense of well-being and personal satisfaction. Creating a motivating environment, taking responsibility for the challenges and stresses of the job, building a supportive team, understanding the AIDS experience, and confronting the effects of grief are also important components in the self-care of the AIDS care giver.

Acquired Immunodeficiency Syndrome↗