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Biomedical subjects

D M Bass

Publications and source records attributed to D M Bass.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1989

Care-related stress. A comparison of spouse and adult-child caregivers in shared and separate households.

This research examines the role that relationship and household arrangement have in explaining the levels of care-related stress effects experienced by spouse and adult-child caregivers in shared and separate residences. Data from 180 spouse and adult-child caregivers were analyzed to identify differences in caregiver health decline, relationship strain, and activity restriction across these settings when the effects of elder impairment, caregiver age, and use of social supports are controlled. Results show that spouse and adult children in shared households experience similar levels of care-related strain. However, comparison of adult children in shared and separate households show considerable cross-setting differences in strain, with those in shared households having significantly greater activity restriction but less relationship strain. These findings have implications for the delivery of social services, specifically for targeting health monitoring, respite, and family counseling services.

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↗
PubMed1984

Experiences with home hospice care: determinants of place of death.

During the past few years the United States has witnessed the growth of hospice care as an alternative approach for the care of the terminally ill. This paper examines a sample of patients who elected to enroll in a home hospice program. Approximately 57 percent of these patients remained at home until death. The other 43 percent chose to return to a facility where they eventually died. Evidence indicates that patients and caregivers who have more difficulty with terminal care at home are more likely to return to a facility. The analysis explores factors that explain why some patients and caregivers have a more troublesome experience with terminal care at home. Four of the factors tested are found to be related to place of death: (1) the number of visits from hospice nurses, (2) the intensity of contact with the hospice nurses, (3) length of time patients are enrolled in the hospice program, and (4) race of the patient. The implications of these findings are discussed and recommendations for delivery of hospice services are suggested.

Age Factors↗
PubMed1984

The needs of hospice patients and primary caregivers.

It would appear that hospice care providers in the program investigated here are highly accurate in their perceptions of their clients' needs. The program therefore is in an excellent position to accomplish its goals. However, findings also suggest that nurses are most accurate in their perceptions of social, emotional, and physical needs. They don't do as well in estimating the importance of material needs, such as financial and legal concerns. Nurses are also more likely to misperceive the importance of religious and spiritual needs. Hospice programs might consider implementing a structural mechanism to assist nurses in the task of understanding these patient and family concerns. Encouraging nurses to routinely inquire about the need for assistance with these issues is one potential remedy. Specific in-service training to teach nurses how to cue in on material and religious needs may also be beneficial. Another approach would be to further integrate staff persons who have specific training in understanding these types of needs into hospice programs. Attorneys, financial consultants, and clergy may need direct contact with patients and families rather than being called into a specific case only after nurses identify the need. Another implication of these results stems from the finding that nurses' perceptions become more similar to caregivers over time. This is particularly true for the assessment of patients' needs. Previous research shows that a substantial proportion of patients do not enter hospice until a few days prior to their deaths.(ABSTRACT TRUNCATED AT 250 WORDS)

Data Collection↗
PubMed1979

Treatment of Dupuytren's contracture by extensive fasciectomy through multiple Y-V--plasty incisions: short-term evaluation of 170 consecutive operations.

The zigzag incision with Y-V closure has unique advantages for the treatment of Dupuytren's disease. Much skin can be mobilized to the longitudinal finger axis. There is rarely a need for skin grafting in spite of full correction of the deformity. This approach, combined with properly applied tamponade bulk dressing, allows for early use of the hand with minimal morbidity.

Dupuytren Contracture↗
PubMed1977

Community-based genetic education, communication channels, and knowledge of Tay-Sachs disease.

In the planning of community-based genetics education campaigns, we cannot assume the existence of a single-minded, passively receptive public, simply waiting to be "educated." Rather, we must consider the impact of preexisting circumstances, notably the differential life-status conditions, the special concerns, and individual motivations of the persons to be educated on their search for information that matters to them. Messages promulgated by mass media educational campaigns on issues in genetics typically do not fall on a homogeneous mass of equally responsive ears and eyes, even if the target population superficially appears to be homogeneous and preselected. Especially institutional sources, (e.g., schools and general education) for males, and social relations (e.g., informal contact among friends) for females are crucial strategic variables affecting transmission and reception of knowledge of Tay-Sachs disease.

Communication↗