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Biomedical subjects

D M Bass

Publications and source records attributed to D M Bass.

At least 19 recordsLinked to original sources
PubMed1996

The moderating influence of service use on negative caregiving consequences.

This investigation adapts the social support conceptual framework to examine the moderating influence of community service use by impaired older persons on the negative consequences of caregiving for informal helpers. The model is modified by defining services as a type of social support that can counteract the stress associated with various care recipient impairments. Results from multivariate analyses of data from 401 caregivers suggest that certain services for care recipients can reduce the adverse effects of certain impairments on informal caregivers. The use of health care service by care recipients who are more disabled is related to lower levels of caregiver depression, health deterioration, and social isolation. Personal care service use consistently offsets the negative effects of care recipients' behavioral problems. Additionally, the use of household service when care recipients exhibit behavioral problems is associated with lower levels of caregiver depression.

Aged↗
PubMed1995

Dansylcadaverine and cytochalasin D enhance rotavirus infection of murine L cells.

Although murine L cells bind and internalize rotavirus as well as permissive cell lines, L cells are essentially nonpermissive for rotaviruses. In nonpermissive cell lines such as L cells, internalized rotavirus fails to uncoat and remains as infectious, double-shelled particles. This block in the infectious cycle can be overcome by direct lipofection of viral particles into the L cell cytoplasm. We hypothesized that the internalized rotavirus particles within L cells are sequestered in the endocytic pathway and are unable to initiate infection. L cells were pretreated with a variety of inhibitors of endocytosis prior to infection with rhesus rotavirus. While agents which inhibit acidification of endosomes had no effect on rotavirus infection, two potential direct inhibitors of vesicular transport, dansylcadaverine and cytochalasin D, enhanced rotavirus infection of L cells 5- to 10-fold. All of the drugs, including both inhibitors of endocytosis and lysosomotrophic agents, significantly reduced infection of L cells by serotype 1 reovirus which is known to infect L cells by the endocytic pathway. Time course studies demonstrated that the drugs were effective in promoting rotavirus infection of L cells in only the early phases of infection. Pretreatment of L cells with dansylcadaverine significantly decreased the number of intact, double-shelled rotavirus particles sequestered within the cells. Inhibition of endocytosis may increase the efficiency of infection of L cells by rotavirus by allowing an increased proportion of attached rotavirus virions to enter cells by a productive route which is probably direct membrane penetration.

Animals↗
PubMed1995

Service use by caregivers of elderly receiving case management.

This article reports on findings from survey interviews with 401 informal caregivers of impaired older persons who were clients of nonprofit case management agencies in Cleveland, OH. The issue addressed is the role of the case manager as a facilitator of caregiver service use when the older person receives case management service. Caregiver services under investigation include respite care, help finding or arranging for service, emotional support or counseling, caregiver education and training, and assistance with other responsibilities such as child care. The study questions are: to what extent do caregivers in this sample utilize these services? What are the predictors of caregiver service use? What implications do the findings have for case management practice?

Adolescent↗
PubMed1994

The influence of a diagnosed mental impairment on family caregiver strain.

This study examines whether a diagnosis of mental impairment of a care recipient influences the strain of family caregiving. Two competing hypotheses, derived from labeling theory, provide alternative views. One posits that a diagnosis reduces strain by linking problematic characteristics of care recipients' impairment to an illness. The competing hypothesis suggests that a diagnosis increases strain by reifying the existence of a progressive chronic condition. LISREL analysis with data from a sample of 576 primary caregivers shows that the diagnosis has an important effect, but this influence varies for different types of strain. Relationship strain and restrictions in social activities are increased for caregivers of diagnosed care recipients. Functional impairment also causes a greater restriction of social activities when a diagnosis has been made. A different pattern emerges for depression, with caregivers in the diagnosed group being less depressed and less negatively affected by care recipients' impaired ability for social interaction, but more depressed by disruptive behavior and functional impairment.

Activities of Daily Living↗
PubMed1993

Murine intestinal mucins inhibit rotavirus infection.

BACKGROUND: Mucin, a population of polymeric glycoproteins, constitutes the primary component of the mucus layer that overlies the gastrointestinal tract. These studies aimed to determine whether murine intestinal mucins inhibit rotavirus infection. METHODS: Murine intestinal mucins were obtained by scraping segments of mouse intestine and purification via CsCl gradient centrifugation and sepharose 4B chromatography. Inhibition of infection was determined by quantitation of immunoperoxidase-stained cells after infection with mucin-rotavirus mixtures. RESULTS: Crude and purified intestinal mucins from suckling and adult mice are potent inhibitors of replication of a simian rotavirus, rhesus rotavirus (RRV), but weak inhibitors of other rotaviruses. In all preparations, colonic mucins were more potent inhibitors of RRV than small intestinal mucins. Suckling mucins neutralized RRV more effectively than adult mucins. In a panel of rotavirus reassortants, susceptibility to mucin inhibition correlated with the ability to hemagglutinate human type O erythrocytes and with RRV gene 4. Murine intestinal mucin inhibited RRV binding to MA104 cells, suggesting inhibition of virus-cell attachment to be the mechanism for neutralization. Mercaptoethanol or neuraminidase inhibited mucins' anti-RRV activities, implying the functional importance of mucins' polymeric structure and sialic acid content. CONCLUSIONS: These findings suggest that intestinal mucins represent a barrier to certain rotavirus infections.

Animals↗
PubMed1992

Predicting the volume of health and social services: integrating cognitive impairment into the modified Andersen framework.

This investigation examined cognitive impairment as a predictor of the volume of community services used by older adults. Predictors of service volume were selected according to the modified Andersen framework and tested with 97 health care and 246 social service clients of a large multiservice agency. Results for health care clients showed that the effects of four predictors differ depending on clients' level of cognitive impairment; living arrangement, presence of secondary caregivers, client depression and task burden of the primary caregiver. No differences in predictor of social service use were observed for cognitively impaired and lucid clients.

Aged↗
PubMed1992

Molecular basis of age-dependent gastric inactivation of rhesus rotavirus in the mouse.

Rotavirus requires specific proteolytic activation by trypsin for efficient replication in tissue culture. To observe the nature of intestinal proteolytic activation of rotavirus in vivo, metabolically labeled rhesus rotavirus (RRV) grown in the presence of trypsin inhibitors was administered to adult and 10-d-old suckling mice by gavage. In the adult stomach, vp4 was cleaved in a manner distinct from in vitro trypsin cleavage. In the suckling stomach, RRV vp4 remains largely uncleaved. The alternative cleavage in the adult stomach was associated with a profound decrease in viral infectivity. vp4 from RRV recovered from the suckling small intestinal lumen was cleaved in a pattern similar or identical to in vitro trypsin-activated virus with bands comigrating with vp5* and vp8*. In contrast, vp4 was not observed in any recognizable form in RRV recovered from adult intestines. Comparison of infectivity of virus recovered from suckling and adult intestines revealed a 10,000-fold decrease in titer in the virus recovered from the adult intestine. In vitro digestions of RRV revealed that pepsin digestion can cleave RRV vp4 and markedly enhance acid-induced loss of rotavirus infectivity. Subsequent digestion with chymotrypsin removes most of the pepsin cleavage products of vp4. Virus injected directly into jejunal loops of adult mice and virus administered orally to adult mice pretreated with antiacid drugs retained infectivity. These studies indicate the development of gastric acid and pepsin secretion may be an important host defense factor in rotavirus gastroenteritis.

Aging↗
PubMed1992

Liposome-mediated transfection of intact viral particles reveals that plasma membrane penetration determines permissivity of tissue culture cells to rotavirus.

Rotaviruses are an important cause of gastroenteritis in human infants. In vivo, rotavirus displays striking cell tropism with viral replication generally restricted to the villus tip enterocytes of the small intestine. We studied a panel of cell lines that vary significantly in their permissivity to rotavirus infection. L cells and HEp2 cells were relatively resistant to rotavirus infection compared with permissive Ma104 cells and HT29 cells. RNA transcription among the cell lines was proportional to antigen synthesis making a translational or posttranslational block an unlikely source of observed differences in susceptibility. All of the cell lines bound and internalized radiolabeled virus equally well, as measured by escape from surface protease treatment. Analysis of the escape of cell bound virus from neutralizing monoclonal antibody revealed that rotavirus did not immediately enter an eclipse phase in nonpermissive cells, but was internalized in an infectious form for several hours, possibly sequestered within endocytic vacuoles. L cells and HEp2 cells were as permissive as Ma104 and HT29 cells when rotavirus infection was mediated by transfection of single- or double-shelled rotavirus particles with cationic liposomes (Lipofectin). Rotavirus cell tropism in tissue culture cells is determined by the ability of infecting virions to traverse the plasma membrane of the cells into the cytoplasmic compartment.

Animals↗
PubMed1991

Identification and partial characterization of a rhesus rotavirus binding glycoprotein on murine enterocytes.

In order to assess the possibility that rotavirus binds to a specific cellular receptor on enterocytes, we have used a viral overlay protein blot assay to study viral binding to murine intestinal brush border membranes (BBM). Infectious double-shelled particles of rhesus rotavirus bound specifically to two approximately 300- and 330-kDa glycoproteins from BBM prepared from suckling mice. Significantly less rotavirus binding was observed when adult BBM were examined. Rats have never been shown to harbor natural group A rotavirus infection and correspondingly, rat BBM showed no rotavirus binding activity. In suckling mice, rotavirus was found to bind to villus tip membranes to a much greater extent than to crypt preparations. Rotavirus binding activity was abolished by treatment of membrane preparations with protease. Analysis by glycolytic digestion of BBM with N- and O-glyconases revealed evidence for both N- and O-linked glycosylation of the rotavirus binding protein. Also neuraminidase digestion showed that O-linked sialic acid residues were required for virus binding. Monoclonal antibodies which immunoprecipitate the 300-kDa viral binding glycoprotein react with the apical surface of suckling but not adult enterocytes by Western blot. Baculovirus-expressed vp4, the rotavirus outer capsid spike protein, bound to the 300- and 330-kDa proteins and competed with rotavirus particles for binding sites. The ability of rotavirus to bind via vp4 to large BBM glycoproteins correlates with in vivo rotavirus cell tropism and host range restriction. Specific host cell receptor expression may be important in rotavirus pathogenesis.

Animals↗
PubMed1991

The influence of caregiving and bereavement support on adjusting to an older relative's death.

This study examines the influence of both caregiving social support to an impaired older relative and bereavement social support to a surviving caregiver on that caregiver's bereavement adjustment. Although past research has considered the link between bereavement support and adjustment to a loved one's death, the influence of support to the care recipient has not been investigated. Analyses of prospective panel data from 73 spouse and adult-child caregivers show caregiving support characteristics to be more important for bereavement adjustment than support provided to the surviving caregiver after their relative's death.

Aged↗
PubMed1990

The transition from caregiving to bereavement: the relationship of care-related strain and adjustment to death.

This study examines two competing hypotheses about the relationship between care-related strain and the difficulty adjusting to the impaired relative's death. One hypothesis, and the limited available empirical evidence, suggests that family members who perceive caregiving as stressful will experience some relief when their relative dies because care responsibilities end. An alternative hypothesis, derived from several conceptualizations, posits the opposite relationship, with greater care-related strain predictive of greater strain during bereavement. Panel data from spouse and adult-child caregivers collected before and after the death support the second hypothesis. Respondents who appraise caregiving as more difficult and those who report more negative caregiving consequences for the family assess bereavement as more difficult and report greater bereavement strain for the family.

Aged↗
PubMed1990

NS35 and not vp7 is the soluble rotavirus protein which binds to target cells.

Recent studies using radiolabeled rotavirus lysates have demonstrated a 35-kilodalton viral protein that binds specifically to the surface of MA104 cells (N. Fukuhara, O. Yoshie, S. Kitakoa, and T. Konno, J. Virol. 62:2209-2218, 1988; M. Sabara, J. Gilchrist, G.R. Hudson, and L.A. Babiuk, J. Virol. 53:58-66, 1985). The binding protein was identified as vp7, an outer capsid glycoprotein and the product of rotavirus gene 9. These studies concluded that vp7 mediated viral attachment to MA104 cells and that the binding of a soluble viral protein to a cell monolayer mirrored the attachment of infectious rotavirus to permissive tissue culture cells. In the process of determining which viral protein adheres to the in vivo target cell in rotavirus infection, the mammalian enterocyte, we found that a similar 35-kilodalton rhesus rotavirus (RRV) protein bound to both MA104 cells and murine enterocytes. However, further analysis of this protein by immunoprecipitation, inhibition of glycosylation, and partial proteolysis showed that it was not the RRV gene 9 product, vp7, but the gene 8 product, NS35. Similar results were obtained by using porcine rotavirus (OSU) and bovine rotavirus (NCDV) strains. Binding studies using the in vitro-expressed products of RRV genes 8 and 9 confirmed these results. Since double-shelled virions inhibited the binding of NS35 to cells, we looked for the presence of this protein in preparations of purified virus. Examination of density gradient-purified virus preparations revealed biochemical and immunological evidence that NS35 copurifies in small amounts with double-shelled virions. Thus, these studies clearly demonstrated that when rotavirus proteins are prepared in a soluble form from infected cells, NS35, and not vp7, binds to the surfaces of MA104 cells and murine enterocytes. The observations do not confirm previous experimental results which supported the hypothesis that vp7 was the viral attachment protein. They are consistent with but do not prove the hypothesis that NS35 functions as the rotavirus attachment protein.

Adsorption↗
PubMed1990

Intraluminal proteolytic activation plays an important role in replication of type 1 reovirus in the intestines of neonatal mice.

Oral inoculation of suckling mice with reovirus serotype 1 (strain Lang) results in the conversion of intact virions to intermediate subviral particles (ISVPs) in the intestinal lumen. Digestion of virus in vitro with chymotrypsin or trypsin reveals two distinct forms of ISVPs, while the predominant species of ISVPs found in the small intestinal lumen appears to be identical to the chymotrypsin product. The in vivo conversion of virions to ISVPs was blocked by pretreatment of mice with protease inhibitors, resulting in inefficient replication of reovirus in intestinal tissue. The early inhibition of viral replication in suckling mice pretreated with protease inhibitors was not observed when suckling mice were inoculated with ISVPs generated by in vitro digestion with either chymotrypsin or trypsin. However, replication was decreased during secondary rounds of replication in mice receiving repeated doses of protease inhibitors, suggesting that luminal proteolytic digestion is important in rendering progeny virions infectious in the gut.

Animals↗
PubMed1989

Home care for elderly persons: linkages between formal and informal caregivers.

Prior research has generally focused on characteristics of elderly persons that predict contact with community services or the volume of services used. In contrast, this study investigates how personal care and home health services are used in relation to assistance from primary kin caregivers. A typology was developed based on task sharing or segregation between kin caregivers and service providers, and four types of informal-formal linkages around these tasks were identified: kin independence, formal service specialization, dual specialization, and supplementation. Findings regarding predictors of the types showed that caregiver and care recipient need variables were most significant in differentiating among them, although caregiver gender also had some discriminatory power.

Activities of Daily Living↗
PubMed1988

Reovirus type I infection of small intestinal epithelium in suckling mice and its effect on M cells.

In 10-day-old mice, reovirus serotype I (reo I) selectively adheres to the apical surface of M cells and penetrates the intestinal epithelium via M cells overlying Peyer's patches before causing disseminated infection. Recently, reo I enteritis has been described in adult mice. We wished to determine if reo I enteritis also occurs in suckling mice and, if so, to determine which major epithelial cell types become infected and where the virus enters epithelial cells other than M cells. Transmission electron microscopy revealed that after oral inoculation of 10-day-old mice, peak infection of M cells preceded that of absorptive and undifferentiated crypt cells. The percentage of M cells in the dome epithelial cell population was reduced more than 4-fold between 4 and 72 hours after reo I inoculation compared with saline-inoculated mice. By 6 days after inoculation, reo I replication was no longer observed and there was a more than 2-fold increase in M cells overlying Peyer's patches domes of reo I-inoculated mice compared with saline controls. By 13 days, control and infected mice had similar percentages of M cells. When incubated with isolated intestinal epithelial sheets, reo I adhered selectively to and was endocytosed via the basal plasma membrane of absorptive cells. Thus, reo I initially penetrates the intestinal epithelium via the apical surface of M cells which become infected. Virions subsequently enter absorptive and crypt cells via their basal surfaces. During the first 3 days of enteritis, the M cell population becomes markedly depleted which may affect the permeability of the mucosal barrier to microorganisms and other antigens as well as influence the host immune response.

Animals↗
PubMed1986

Symptoms of mental impairment among elderly adults and their effects on family caregivers.

Research that has examined the relationship between caregiving stress and elders' symptoms of mental impairment has focused primarily on cognitive incapacity. This research expands the symptoms of mental impairment to include caregivers' reports of problems in elders' social functioning and the presence of disruptive behavior, in addition to the traditional measure of cognitive incapacity. Results from a study of 614 families living with and caring for an impaired elder show cognitive incapacity to have a less important direct effect on caregiving stress than disruptive behavior and impaired social functioning. Cognitive incapacity does have an important indirect effect through its influence on disruptive behavior and social functioning.

Activities of Daily Living↗