Prevalence and impact of caregiving: a detailed comparison between dementia and nondementia caregivers.

Analyzing data from more than 1,500 family caregivers from the 1996 National Caregiver Survey, this study documents the ways in which dementia care is different from other types of family caregiving. Not only do dementia caregivers spend significantly more hours per week providing care than nondementia caregivers, they also report greater impacts in terms of employment complications, caregiver strain, mental and physical health problems, time for leisure and other family members, and family conflict. Differential impacts remain even after controlling for intensity of caregiving involvement and sociodemographic factors. Study findings suggest the need to tailor programs and services to the unique challenges faced by dementia caregivers.

Calcium mobilization-associated and independent cytosolic acidification elicited in tandem with Na+/H+ exchanger activation in target cell-adherent human NK cells.

Flow cytometry was used to identify mechanisms by which human NK cells regulate intracellular pH (pHi) and to investigate the relationship between NK cell pHi and cytolytic function. Temporally resolved determinations of pHi were simultaneously made in NK cells that formed conjugates with target cells (NKC) and unconjugated NK cells (NKU) on the basis of the red/orange fluorescence emission ratio of the pH indicator seminapthylrhodafluor-1. Two pHi regulatory mechanisms were identified in NK cells: 1) a HCO3-/Cl- antiport that promoted pHi changes in response to variation of extracellular HCO3- and Cl- but not Na+ ion concentrations, was sensitive to stilbene derivatives 4,4'-diisothiocyanatostilbene sulfonic acid and 4-acetamido-4'-isothyocyanotostilbene-2-2'-disulfonic acid, and exhibited similar activity in NKC and NKU, and 2) a Na+/H+ exchanger that promoted pHi changes in response to extracellular Na+ ion concentration changes and was sensitive to dimethylamiloride (DMA), permeable to Na+ and Li+ but not K+ or N-methyl-D-glucamine, and quiescent in NKU but activated in target cell-adherent NKC. When Na+/H+ exchange was blocked with 10 microM DMA, the pHi of NKC bound to NK-sensitive K562 target cells progressively decreased for 3 to 4 min, then stabilized at 0.1 to 0.15 pH units below the pHi of NKU. A significant temporal decline in NKC pHi also occurred in the nominal absence of extracellular Ca2+ (0.07 +/- 0.02 pH units) and when NKC formed conjugates with NK-resistant B lymphoblastoid target cells that failed to mobilize NK cell Ca2+ (0.07 +/- 0.01 pH units) (mean +/- SD). However, the magnitude of the NKC cytosolic acidification response was consistently reduced (42 +/- 4 and 44 +/- 6%, respectively) under these Ca2+ flux response-limiting conditions. Thus, adhesion to target cells triggered two pHi-related responses in NK cells: 1) a decline in pHi which exhibited both Ca2+ mobilization-dependent and -independent components, and 2) Na+/H+ exchanger activation by which acid production was neutralized. Manipulations of HCO3- and DMA that clamped NKC pHi at values ranging from 6.8 to 7.2 failed to significantly influence NK cell cytolytic function. By contrast, isosmotic replacement of extracellular Na+ with NMDG resulted in a 57 +/- 22% inhibition of NK cell-mediated cytolysis (n = 8, p < 0.01). NKC pHi declined to 6.8 to 6.9 under these conditions, but this was not the apparent basis of impaired cytolysis because sustained elevation of NKC pHi by addition of dimethylamine failed to significantly reverse inhibition.(ABSTRACT TRUNCATED AT 400 WORDS)

Resolution of adhesion- and activation-associated components of monoclonal antibody-dependent human NK cell-mediated cytotoxicity.

Flow cytometry was used to investigate two functional parameters of human natural-killer (NK) cell-mediated antibody-dependent cellular cytotoxicity (ADCC): (i) the frequency of NK cells which formed conjugates (NKC) with autologous monoclonal antibody (mAb)-coated lymphocyte target cells, a measure of the avidity of CD16-dependent cell-cell adhesion, and (ii) the rise in the intracellular concentration of ionized calcium ([Ca2+]i) elicited in NKC by contact with target cells, a measure of CD16-dependent NK cell activation. For each of four rat IgG2b mAb directed against target cell antigens CDw52, CD5, CD45, and class I HLA, there existed quantitatively similar relationships between ADCC and rise in NKC[Ca2+]i but significant inter-mAb differences with respect to the ADCC vs the NKC frequency relationship. Cytolytic efficiencies of mAb appeared to be determined at the level of the NK cell, dependent upon CD16 and LFA-1, but restricted with respect to quantitative levels of NKC[Ca2+]i. In concert with this notion, targets coated with an IgG1 isotype-switch variant alpha CDw52 mAb promoted significant conjugate formation but failed to elicit a rise in NKC[Ca2+]i or ADCC. Thus, Fc regions of antibodies make contacts with NK cell CD16 which may strengthen cell-cell adhesion without eliciting an activation stimulus, a finding which supports a complexity of CD16 functional regulation of probable significance in the clinical consequences of antibody responses or therapeutic mAb manipulations.

Relationship between target cell recognition and temporal fluctuations in intracellular Ca2+ of human NK cells.

Temporal changes in intracellular Ca2+ concentration, [Ca2+]i, of resting human peripheral blood NK cells in response to target cell binding were evaluated by flow cytometry. [Ca2+]i was significantly elevated in PBL and purified NK cells bound to NK-sensitive K562 and HSB2 target cells, but not in those bound to NK-resistant MD1 B-lymphoblastoid cells. Thus, a) the ability of a target cell to elicit a Ca2+ flux response correlated with its sensitivity to lysis of NK cells, and b) adhesion alone was not a sufficient stimulus for response induction. Conjugates of NK cells bound to K562 target cells were sorted onto agarose-coated slides on the basis of relative NK cell [Ca2+]i and evaluated in 19-hr single cell agarose cytotoxicity assays. In contrast to those with basal levels of [Ca2+]i, NK cells with elevated [Ca2+]i bound more strongly to target cells, as judged by the stability of conjugates to sort-related shear forces (p less than 0.01), and more frequently killed the target cell to which they were attached (p less than 0.05). Temporal fluctuations in [Ca2+]i were observed in target-bound NK cells in both the presence and absence of extracellular Ca2+. Thus, influx of extracellular Ca2+ and release of Ca2+ from internal stores both appeared to contribute to the NK cell Ca2+ flux response triggered by adhesion to appropriate target cells. These results support the hypothesis that such fluctuations in NK cell [Ca2+]i constitute an early signal flagging the occurrence of NK cell recognition.

Comprehensive quality assessment approach for flow cytometric immunophenotyping of human lymphocytes.

Flow cytometric immunophenotypic (IPT) evaluation has become an important adjunct to clinical patient management and epidemiological studies. This has precipitated a need for stringent quality assessment (QA) procedures to ascertain data integrity. We evaluated a QA approach to monitor all elements of the immunophenotyping process, inclusive of blood collection and processing procedures as well as of staining reagent and instrument performance. Central to our approach was preparation each day, in parallel with clinical analytes, of lymphocytes from healthy donors, selected from a 15 donor panel. IPT parameters evaluated over a 19 month period included frequencies of CD3+, CD4+, CD8+, and CD20+ lymphocytes and the ratio of CD4+ to CD8+ lymphocytes. The sensitivity for analytical error detection was reflected by median coefficients of variation of these parameters within individual panel donors, which were 4.1%, 4.5%, 3.9%, 8.2%, and 10.1%, respectively. IPT parameter values were determined each day for two of the panel donors, then averaged and standardized to obtain a quality or Q variate, which was the basis of QA. Error detection sensitivity decreased 0.6-1.7% and the number of false rejections increased 1.2-3.3% when one panel donor rather than two was used daily for QA. This study also illuminated important aspects of what constitutes the norm for longitudinal IPT parameter variation in healthy individuals including: 1) a generally low degree of temporal parameter variation within individual donors, but 2) significant differences between donors with respect to variance estimates for CD3+ and CD8+ lymphocyte frequencies and CD4+/CD8+ lymphocyte ratios, and 3) an apparent seasonal pattern of variation in CD4+ T-cell frequencies.

Instrumented measurement of human joint motion.

Accurate measurement of human joint motion is essential to the design and evaluation of internal joint prostheses and artificial limb replacements. A triaxial electrogoniometer instrumented by three miniature precision potentiometers was developed to fulfill this task. A special linkage was used to attach this apparatus externally to the joint. Three-dimensional angular motion following the classical Eulerian angle definition was measured in real time. The error due to exoskeletal attachment was corrected by the method of 4 x 4 matrix. This technique is now being routinely used for objective functional evaluation on the patients with abnormal hip, knee and ankle joints as well as lower extremity amputees fitted with artificial limbs.

Semantic memory for metaphor: The conceptual base hypothesis.

The idea that people can encode and use an extremely abstract and general form of a complex linguistic (proverb) input-a conceptual base-was examined in two experiments. In Experiment I, each proverb was accompanied by either a conceptually related (good, mediocre, or poor) or an unrelated interpretation. The related interpretations were more effective recall prompts than were the unrelated interpretations, but only for high-imagery proverbs. In Experiment II, subjects wrote interpretations of the proverbs and then received either the proverb subject-noun or a brief story as a prompt. As was the case for the interpretations in Experiment I, the stories did not share any major vocabulary or propositional structure with their proverb source. Nonetheless, the stories were as effective as the nouns. Also, quality of proverb interpretation and of recall performance were positively related, with the correlations involving low-imagery proverbs, and stories, tending to be higher. Both experiments provided support for the conceptual-base notion, and underlined the importance of interpretive context, but more definitive evidence is needed.