Biochemical mechanisms that interact with membrane-associated IL-1 RII (60-kDa decoy) receptors in populations of adherent macrophages and vascular endothelium

The aim of this investigation was to identify the potential biochemical mechanisms that alter the integrity of membrane-associated IL-1 RII (decoy) receptor complexes expressed by populations of adherent macrophages and vascular endothelium. The initial research strategy utilized to achieve this objective involved delineating the ability of macrophage activation or exposure of macrophages and vascular endothelium to a spectrum of enzyme proteases to influence the expression of membrane-associated IL-1 RII (decoy) or generate soluble fragments of this receptor complex. Results from these investigations revealed that stimulated macrophages displayed proportional increases in both the expression of membrane-associated IL-1 RII (decoy) and release of soluble receptor fragments. Exposure of macrophages and vascular endothelium to the reference proteases discovered the ability of cathepsin-D to biochemically deplete membrane-associated IL-1 RII (decoy) in addition to generating soluble fragments of this receptor complex. Complementary investigations isolated a carboxyl/aspartate protease from activated macrophages utilizing pepstatin-A affinity chromatography. Exposure of vascular endothelium to pepstatin-A binding proteins resulted in a detectable depletion of membrane-associated IL-1 RII (decoy) and generation of soluble receptor fragments. Evaluation of pepstatin-A binding proteins by SDS-PAGE identified a primary protein fraction with a molecular mass of 47-52 kDa that closely correlates with the known molecular size of leukocyte cathepsin-D fractions. Macrophage pepstatin-A binding protein fractions evaluated by nondenaturing haemoglobin-substrate PAGE (Hb-PAGE) analysis detected a lucent proteolytic band at 47-52 kDa. Macrophage pepstatin-A binding proteins also hydrolyzed a synthetic enzyme-specific substrate that selectively recognizes cathepsin-D biochemical activity. In conclusion, the leukocyte carboxyl/aspartate protease cathepsin-D can biochemically alter the integrity and generate soluble fragments of membrane-associated IL-1 RII (60-kDa decoy) receptor complexes expressed by macrophages and vascular endothelium.

Biochemical alteration of membrane-associated IL-6 RI (80-kDa) in adherent macrophages and vascular endothelium

The potential biochemical mechanisms that mediate the 'shedding' of soluble IL-6 RI (80-kDa) receptor fragments in populations of adherent macrophages were explored. Stimulated macrophages displayed proportional increases in both the expression of membrane-associated IL-6 RI (80-kDa) and the release of soluble receptor fragments. The use of protease inhibitors implicated thiol/cysteine and carboxyl/aspartate proteases in this process. Cathepsin-D depleted membrane-associated IL-6 RI (80-kDa) complexes and generated soluble receptor fragments. A carboxyl/aspartate protease from activated macrophages isolated utilizing pepstatin-A affinity chromatography, was also found to affect membrane-associated IL-6 RI (80-kDa) complexes and generate soluble receptor fragments. Most likely, this fraction corresponded to cathepsin-D based upon its origin, pepstatin-A binding avidity, Hb-PAGE zymography, and hydrolysis of an enzyme-specific substrate. We conclude that cathepsin-D can generate soluble fragments of IL-6 RI (80-kDa) expressed by both macrophages and vascular endothelium.

Partial T-cell activation and anergy induction by polyclonal antithymocyte globulin

BACKGROUND

Polyclonal antithymocyte globulins have been assumed to deplete or sequester immunocompetent T cells. We investigated the hypothesis that anti-human thymocyte globulin (ATGAM)-mediated immunosuppression is delivered via nondepletive, immunologically specific actions as a consequence of simultaneous engagement of multiple T cell receptors.

METHODS

Purified T cells obtained from healthy volunteers or renal transplant recipients receiving their first dose of ATGAM were evaluated for proliferative responses and cell-mediated lympholysis. ATGAM binding and receptor expression were determined by flow cytometry. Cytokines and ATGAM levels were measured by enzyme-linked immunosorbent assay.

RESULTS

ATGAM-treated T cells showed significant dose-dependent inhibition of proliferation in vitro at concentrations comparable to those measured in patients. Effectors raised after ATGAM treatment failed to develop cytotoxicity. Supernatant interleukin (IL)-2 levels in ATGAM-treated cultures were significantly reduced (P<0.01 vs. control). IL-4 was not significantly altered. In vivo studies confirmed significant ATGAM-mediated inhibition of proliferative responses. Concanavalin A and OKT3-driven proliferation were reduced 30-60% by ATGAM. Flow cytometry showed that ATGAM recognized multiple cell surface receptors and resulted in markedly increased IL-2R and CD28 expression in the absence of proliferation, demonstrating partial T-cell activation. ATGAM synergized with phorbol myristate acetate to produce strong proliferation, which suggests that it provides a calcium-based signal resulting in anergy.

CONCLUSIONS

ATGAM recognizes and cross-links multiple cell surface receptors and costimulator molecules on human T cells. Simultaneous engagement by ATGAM in the context of allogeneic or mitogenic stimulation leads to partial T-cell activation and anergy.

Short-term administration of tall oil phytosterols improves plasma lipid profiles in subjects with different cholesterol levels

To assess the short-term cholesterol-lowering potential of sitostanol-containing tall oil plant sterols, 22 subjects consumed fixed-food diets over two 10-day periods with or without 21.2 mg/kg body weight/d tall oil phytosterols (sitosterol 62%, sitostanol 21%, campesterol 16%, and campestanol 1%) in a randomized crossover study design. On day 10 of each diet, plasma lipoprotein cholesterol levels, plasma phytosterol concentrations, and cholesterol biosynthesis rates were determined. Total cholesterol (TC) and low-density lipoprotein (LDL) cholesterol levels were lower (P < .01) after administration of tall oil phytosterol (4.7 +/- 0.3 and 3.0 +/- 0.3 mmol/L, respectively) versus placebo (5.0 +/- 0.3 and 3.2 +/- 0.3 mmol/L, respectively). Tall oil treatment had no effect on the plasma high-density lipoprotein (HDL) cholesterol level (1.1 +/- 0.1 mmol/L) versus placebo (1.1 +/- 0.1 mmol/L). Similarly, plasma triglyceride (TG) levels did not differ between tall oil (1.3 +/- 0.2 mmol/L) and placebo (1.4 +/- 0.2 mmol/L) treatments. Plasma campesterol (15.8 +/- 3.7 mmol/mol cholesterol) and sitosterol (6.0 +/- 2.1 mmol/mol cholesterol) levels were not different after tall oil treatment versus placebo treatment (15.4 +/- 2.3 and 6.4 +/- 2.0 mmol/mol cholesterol, respectively). Plasma sitostanol levels were essentially undetectable. No difference was observed in cholesterol biosynthesis between tall oil (0.045 +/- 0.004 pools/d) and placebo (0.034 +/- 0.004 pools/d) treatments; however, the effect of treatments in subjects with different cholesterol levels varied. In subjects with lower cholesterol values, the red blood cell cholesterol fractional synthesis rate (FSR) increased from 0.0291 +/- 0.0054 pools/d after placebo to 0.0509 +/- 0.0049 pools/d (P < .05) after phytosterol treatment. In subjects with higher cholesterol values, the red blood cell cholesterol FSR did not change significantly after treatment. These results demonstrate the short-term efficacy of tall oil plant sterols as cholesterol-lowering agents.

A systems approach to asthma care

This two-year asthma intervention focuses on provider education emphasizing early diagnosis of asthma, early use of oral steroids, proper use of inhalation devices, objective monitoring of patient status, and use of daily preventive treatment. Patient education is an integral part of treatment. This approach supports the primary care physician as the provider and coordinator of care by supplying monitoring and treatment devices, books, diaries, home care services, and allergy consultation. It also manifests a systems approach to asthma care in its reliance on a nurse case manager who oversees patient and family support network.

Thermal balance and metabolic rate during upper respiratory tract infection in infants

Sequential recordings were made in the first five months after birth of metabolic rate, environmental temperature, and body temperature during sleep at home in 17 infants, each with an older sibling. Further recordings were made whenever an older sibling developed an upper respiratory tract infection (URTI), again four to six days later, and again two weeks later, aiming to achieve recordings before, during, and after an URTI in the infant. The temperature of the room and wrapping of the infant were determined according to their usual practice by the parents. Parents added appropriate wrapping to achieve thermal neutrality based on our calculated values and the measured oxygen consumption. In five of the six infants who developed an URTI in the first three months after birth there was no change or a decrease in metabolic rate at the time of the infection; for infants older than 3 months the metabolic rate increased in three of the five episodes recorded. Peripheral skin temperature decreased at the time of URTI at all ages, though in the older infants it usually increased in parallel with rectal temperature during the latter part of the night, when pyrexia was most common. Infants thus respond to URTI by heat conservation. In the younger infants the lower metabolic rate and the further decrease in this rate with URTI means that fever is rare, and their temperature may decrease on infection. In the older infants the increase in metabolic rate (from an already higher baseline) may result in fever. These differences may contribute to the increased vulnerability of the older infants to heat stress, particularly at the time of acute viral infections.

Knowledge and skills needed for collaborative work

The need for collaboration and cooperation in health care delivery is not news. But one of the first requests often made by leaders and others promoting collaborative work in organizations is for a "facilitator course." As the authors developed more knowledge about the real need, they understood that many of the barriers to collaborative work and learning in organizations can be reduced only by the top leaders, not by expert facilitators. The central knowledge that leaders need to support collaborative work is appreciation of work as a system.

Cot death: follow up support for families with subsequent children

Sudden infant death is the major cause of post-neonatal mortality in industrialised countries. For parents, the sudden, unexpected and inexplicable death of their baby can be devastating. Long-term support and follow-up care is needed. In the second of two articles Alison Stewart, Peter Fleming and Thelma Howell describe a follow-up support scheme offered to parents in Avon who have experienced a cot death and subsequently go on to have another child or children.

Geriatricians' attitudes toward assisting suicide of dementia patients

OBJECTIVE

To identify geriatricians' attitudes toward assisting suicide of dementia patients, with particular reference to the case of Janet Adkins/Dr. Kevorkian.

DESIGN

Mailed questionnaire survey.

SETTING

Four distinct geographical regions of the US: Far West, Midwest, Southeast, and Northeast.

PARTICIPANTS

All 1,381 ABIM-certified internist geriatricians in the four regions; 727 (52.6%) responded.

MAIN OUTCOME MEASURES

Positive, negative, or unsure responses to questionnaire items; comparison of responses between geographical regions.

RESULTS

Sixty-six percent of respondents felt that Dr. Kevorkian's assistance of Janet Adkins' suicide was not justifiable, while 14% stated it was morally justifiable. Twenty-nine percent felt Janet Adkins' decision to commit suicide was morally wrong, while 49% stated it was not morally wrong. If the responding geriatricians themselves were diagnosed as having a dementing illness, 41% would consider suicide a possible option; 39% would not consider suicide. Twenty-six percent favored easing restrictions on physician-assisted suicide of competent dementia patients, while 57% opposed this. If current restrictions were eased, 21% would consider assisting suicide of competent dementia patients, and 66% would not. Respondents' attitudes showed some significant (P less than or equal to 0.05) variations by geographical region. Where regional differences were observed, respondents in the Midwest tended to show more conservative attitudes toward physician-assisted suicide than those in the Far West and Northeast.

CONCLUSIONS

Most responding geriatricians would not consider assisting suicide of dementia patients, and most oppose easing restrictions on physician-assisted suicide. Many, however, could accept the (unassisted) suicide of a competent dementia patient, and many would consider suicide themselves if stricken with dementia.

Occupational therapy in geriatric mental health

Elderly persons with psychiatric disorders often experience a variety of functional deficits that affect their independence, safety, and activity level. The occupational therapist's role in addressing these needs is discussed, as are the possibilities for improvement of the elderly person's autonomy, safety, and integrity. Barriers to optimal service provision in the health care and social service systems as well as in occupational therapy are addressed.

Dangerous behavior in a demented patient. Preserving autonomy in a patient with diminished competence

When a cognitively-impaired elderly man nearly caused a serious fire at home through his inappropriate use of a gas oven, the incident raised questions about his capacity to live alone. Although he clearly wanted to preserve his independence, the health care team felt obligated to assure his safety. The following discussion of dangerous behavior in a demented elderly man elicits and portrays these conflicting values, and highlights the physician's obligations in such ethically and legally complex situations.