Microsecond dynamics control the HIV-1 Envelope conformation

The HIV-1 Envelope (Env) glycoprotein facilitates host cell fusion through a complex series of receptor-induced structural changes. Although remarkable progress has been made in understanding the structures of various Env conformations, microsecond timescale dynamics have not been studied experimentally. Here, we used time-resolved, temperature-jump small-angle x-ray scattering to monitor structural rearrangements in an HIV-1 Env SOSIP ectodomain construct with microsecond precision. In two distinct Env variants, we detected a transition that correlated with known Env structure rearrangements with a time constant in the hundreds of microseconds range. A previously unknown structural transition was also observed, which occurred with a time constant below 10 μs, and involved an order-to-disorder transition in the trimer apex. Using this information, we engineered an Env SOSIP construct that locks the trimer in the prefusion closed state by connecting adjacent protomers via disulfides. Our findings show that the microsecond timescale structural dynamics play an essential role in controlling the Env conformation with impacts on vaccine design.

A molecular dynamics study of cell-penetrating peptide transportan-10 (TP10): Binding, folding and insertion to transmembrane state in zwitterionic membrane

Transportan 10 (TP10) is a 21-residue, cationic, α-helical cell-penetrating peptide that can be used as a delivery vector for various bioactive molecules. Based on recent confocal microscopy studies, it is believed that TP10 can translocate across neutral lipid membrane passively, possibly as a monomer, without the formation of permanent pore. Here, we performed extensive molecular dynamics (MD) simulations of TP10W (Y3W variant of TP10) to find the microscopic details of binding, folding and insertion of TP10W to transmembrane state in POPC bilayer. Binding study with CHARMM36 force field showed that TP10W initially binds to the membrane surface in unstructured configuration, but it spontaneously folds into α-helical conformation under the lipid head groups. Further insertion of TP10W, changing from a surface bound state to a vertically oriented transmembrane state, was investigated via umbrella simulations. The resulting free energy profile shows a relatively small barrier between two states, suggesting a possible translocation pathway as a monomer. In fact, unbiased simulation of transmembrane TP10W revealed how a charged Lys side chain can move from one leaflet to the other without a significant free energy cost. Finally, we compared the results of TP10W simulations with those of point mutated variants (TP10W-K12A18 and TP10W-K19L) to understand the effect of charge distribution on the peptide. It was observed that such a conservative mutation can cause noticeable changes in the conformations of both surface bound and transmembrane states. The results of present study will be discussed in relation to the experimentally observed activities of TP10W against neutral membrane.

Microsecond dynamics control the HIV-1 envelope conformation

The HIV-1 Envelope (Env) glycoprotein facilitates host cell fusion through a complex series of receptor-induced structural changes. Although significant progress has been made in understanding the structures of various Env conformations and transition intermediates that occur within the millisecond timescale, faster transitions in the microsecond timescale have not yet been observed. In this study, we employed time-resolved, temperature-jump small angle X-ray scattering to monitor structural rearrangements in an HIV-1 Env ectodomain construct with microsecond precision. We detected a transition correlated with Env opening that occurs in the hundreds of microseconds range and another more rapid transition that preceded this opening. Model fitting indicated that the early rapid transition involved an order-to-disorder transition in the trimer apex loop contacts, suggesting that conventional conformation-locking design strategies that target the allosteric machinery may be ineffective in preventing this movement. Utilizing this information, we engineered an envelope that locks the apex loop contacts to the adjacent protomer. This modification resulted in significant angle-of-approach shifts in the interaction of a neutralizing antibody. Our findings imply that blocking the intermediate state could be crucial for inducing antibodies with the appropriate bound state orientation through vaccination.

Ileal bile acid transporter inhibition in Cyp2c70 KO mice ameliorates cholestatic liver injury

Cyp2c70 is the liver enzyme in rodents responsible for synthesis of the primary 6-hydroxylated muricholate bile acid (BA) species. Cyp2c70 KO mice are devoid of protective, hydrophilic muricholic acids, leading to a more human-like BA composition and subsequent cholestatic liver injury. Pharmacological inhibition of the ileal BA transporter (IBAT) has been shown to be therapeutic in cholestatic models. Here, we aimed to determine if IBAT inhibition with SC-435 is protective in Cyp2c70 KO mice. As compared to WT mice, we found male and female Cyp2c70 KO mice exhibited increased levels of serum liver injury markers, and our evaluation of liver histology revealed increased hepatic inflammation, macrophage infiltration, and biliary cell proliferation. We demonstrate serum and histologic markers of liver damage were markedly reduced with SC-435 treatment. Additionally, we show hepatic gene expression in pathways related to immune cell activation and inflammation were significantly upregulated in Cyp2c70 KO mice and reduced to levels indistinguishable from WT with IBAT inhibition. In Cyp2c70 KO mice, the liver BA content was significantly increased, enriched in chenodeoxycholic acid, and more hydrophobic, exhibiting a hydrophobicity index value and red blood cell lysis properties similar to human liver BAs. Furthermore, we determined IBAT inhibition reduced the total hepatic BA levels but did not affect overall hydrophobicity of the liver BAs. These findings suggest that there may be a threshold in the liver for pathological accretion of hydrophobic BAs and reducing hepatic BA accumulation can be sufficient to alleviate liver injury, independent of BA pool hydrophobicity.

Doxorubicin for treatment of histiocytic sarcoma in dogs: 31 cases (2003-2017)

OBJECTIVE

To evaluate the efficacy of doxorubicin for treatment of histiocytic sarcoma (HS) in dogs, whether administered as the sole treatment or as an adjunct to surgery or radiation therapy.

ANIMALS

31 client-owned dogs with localized or disseminated HS examined between 2003 and 2017.

PROCEDURES

Medical records were reviewed retrospectively, and data were collected. The Kaplan-Meier method was used to estimate time-to-progression from the date of first doxorubicin administration and survival time from initial diagnosis. Factors that could be associated with poorer outcomes with doxorubicin treatment were analyzed with log-rank tests.

RESULTS

The objective response rate (ORR) was 26%. When stratified by disease status, dogs with localized and disseminated forms experienced 43% and 21% ORRs, respectively. Median time to progression after initiating doxorubicin treatment (n = 30 dogs) was 42 days. Median survival time from initial diagnosis to death (n = 29 dogs) was 169 days. Complete responses were obtained in only 2 dogs that had localized disease and received multimodality therapy.

CLINICAL RELEVANCE

Benefits of doxorubicin administration in canine HS are modest, with a limited ORR and delay in tumor progression, and are comparable to effects attained with other single-agent regimens.

Marginal Zone B Cells Induce Alloantibody Formation Following RBC Transfusion

Red blood cell (RBC) alloimmunization represents a significant immunological challenge for some patients. While a variety of immune constituents likely contribute to the initiation and orchestration of alloantibodies to RBC antigens, identification of key immune factors that initiate alloantibody formation may aid in the development of a therapeutic modality to minimize or prevent this process. To define the immune factors that may be important in driving alloimmunization to an RBC antigen, we determined the specific immune compartment and distinct cells that may initially engage transfused RBCs and facilitate subsequent alloimmunization. Our findings demonstrate that the splenic compartment is essential for formation of anti-KEL antibodies following KEL RBC transfusion. Within the spleen, transfused KEL RBCs are found within the marginal sinus, where they appear to specifically co-localize with marginal zone (MZ) B cells. Consistent with this, removal of MZ B cells completely prevented alloantibody formation following KEL RBC transfusion. While MZ B cells can mediate a variety of key downstream immune pathways, depletion of follicular B cells or CD4 T cells failed to similarly impact the anti-KEL antibody response, suggesting that MZ B cells may play a key role in the development of anti-KEL IgM and IgG following KEL RBC transfusion. These findings highlight a key contributor to KEL RBC-induced antibody formation, wherein MZ B cells facilitate antibody formation following RBC transfusion.

Antibody-mediated immune suppression by antigen modulation is antigen-specific

Alloantibodies developing after exposure to red blood cell (RBC) alloantigens can complicate pregnancy and transfusion therapy. The only method currently available to actively inhibit RBC alloantibody formation is administration of antigen-specific antibodies, a phenomenon termed antibody-mediated immune suppression (AMIS). A well-known example of AMIS is RhD immune globulin prophylaxis to prevent anti-D formation in RhD- individuals. However, whether AMIS is specific or impacts alloimmunization to other antigens on the same RBC remains unclear. To evaluate the specificity of AMIS, we passively immunized antigen-negative recipients with anti-KEL or anti-hen egg lysozyme (HEL) antibodies, followed by transfusion of murine RBC expressing both the HEL-ovalbumin-Duffy (HOD) and human KEL antigens (HOD × KEL RBC). Significant immunoglobulin G deposition on transfused HOD × KEL RBC occurred in all passively immunized recipients. Complement deposition and antigen modulation of the KEL antigen occurred on transfused RBC only in anti-KEL-treated recipients, whereas HEL antigen levels decreased only in the presence of anti-HEL antibodies. Western blot analysis confirmed the specificity of antigen loss, which was not attributable to RBC endocytosis and appears distinct for the 2 antigens. Specifically, removal of KEL was attenuated by clodronate treatment, whereas loss of HEL was unaffected by clodronate in vivo but sensitive to protease treatment in vitro. Antigen-specific modulation correlated with antigen-specific AMIS, with anti-KEL treated recipients forming antibodies to the HOD antigen and anti-HEL-treated recipients developing antibodies to the KEL antigen. Together, these results demonstrate that passively administered antibodies can selectively inhibit the immune response to a specific antigen.

Coupling between an electrostatic network and the Zn2+ binding site modulates Hv1 activation

The voltage sensor (VS) domain in Hv1 proton channels mediates a voltage-dependent and H+-selective "aqueous" conductance (GAQ) that is potently modulated by extracellular Zn2+ Although two conserved His residues are required for Zn2+ effects on GAQ gating, the atomic structure of the Zn2+ coordination site and mechanism by which extracellular Zn2+ stabilizes a closed-state conformation remain unknown. Here we use His mutagenesis to identify residues that increase Zn2+ potency and are therefore likely to participate in first solvation shell interactions with Zn2+ Experimental Zn2+-mapping data were then used to constrain the structure of a new resting-state Hv1 model (Hv1 F). Molecular dynamics (MD) simulations show how protein and water atoms directly contribute to octahedral Zn2+ coordination spheres in Zn2+-bound and -unbound Hv1 F models. During MD simulations, we observed correlated movements of Zn2+-interacting side chains and residues in a highly conserved intracellular Coulombic network (ICN) that contains highly conserved Arg "gating charges" in S4 as well as acidic "counter-charges" in S2 and S3 and is known to control VS activation, suggesting that occupancy of the extracellular Zn2+ site is conformationally coupled to reorganization of the ICN. To test this hypothesis, we neutralized an ICN Glu residue (E153) and show that in addition to shifting GAQ activation to more negative voltages, E153A also decreases Zn2+ potency. We speculate that extracellular gating-modifier toxins and other ligands may use a generally similar long-range conformational coupling mechanism to modulate VS activation in related ion channel proteins.

Coarse-grained simulations of hemolytic peptide δ-lysin interacting with a POPC bilayer

δ-lysin, secreted by a Gram-positive bacterium Staphylococcus aureus, is a 26-residue membrane active peptide that shares many common features with antimicrobial peptides (AMPs). However, it possesses a few unique features that differentiate itself from typical AMPs. In particular, δ-lysin has zero net charge, even though it has many charged residues, and it preferentially lyses eukaryotic cells over bacterial cells. Here, we present the results of coarse-grained molecular dynamics simulations of δ-lysin interacting with a zwitterionic membrane over a wide range of peptide concentrations. When the peptides concentration is low, spontaneous dimerization of peptides is observed on the membrane surface, but deep insertion of peptides or pore formation was not observed. However, the calculated free energy of peptide insertion suggests that a small fraction of peptides is likely to be present inside the membrane at the peptide concentrations typically seen in dye efflux experiments. When the simulations with multiple peptides are carried out with a single pre-inserted transmembrane peptide, spontaneous pore formation occurs with a peptide-to-lipid ratio (P/L) as low as P/L=1:42. Inter-peptide salt bridges among the transmembrane peptides seem to play a role in creating compact pores with very low level of hydration. More importantly, the transmembrane peptides making up the pore are constantly pushed to the opposite side of the membrane when the mass imbalance between the two sides of membrane is significant. Thus, the pore is very dynamic, allowing multiple peptides to translocate across the membrane simultaneously.

Proton currents constrain structural models of voltage sensor activation

The Hv1 proton channel is evidently unique among voltage sensor domain proteins in mediating an intrinsic 'aqueous' H⁺ conductance (G_AQ). Mutation of a highly conserved 'gating charge' residue in the S4 helix (R1H) confers a resting-state H⁺ 'shuttle' conductance (G_SH) in VGCs and Ci VSP, and we now report that R1H is sufficient to reconstitute G_SH in Hv1 without abrogating G_AQ. Second-site mutations in S3 (D185A/H) and S4 (N4R) experimentally separate G_SH and G_AQ gating, which report thermodynamically distinct initial and final steps, respectively, in the Hv1 activation pathway. The effects of Hv1 mutations on G_SH and G_AQ are used to constrain the positions of key side chains in resting- and activated-state VS model structures, providing new insights into the structural basis of VS activation and H⁺ transfer mechanisms in Hv1.

Canine acute leukaemia: 50 cases (1989-2014)

Acute leukaemia (AL) is a bone marrow malignancy of hematopoietic progenitors that historically is poorly responsive to treatment. With the widespread adoption of dose-intense chemotherapy, more human patients attain long-term survivals, but whether comparable progress has been made in canine AL is unknown. To investigate this question, medical records from three academic veterinary hospitals were reviewed. Fifty dogs met the criteria for AL, having excess circulating or marrow blasts, a major cytopenia(s), and no substantial lymphadenopathy. Thirty-six dogs received cytotoxic chemotherapy; 23 achieved a complete or partial response for a median of 56 days (range, 9-218). With failure or relapse, 14 dogs were rescued. Median survival with treatment was poor at 55 days (range, 1-300). Untreated (n = 6) and palliatively-treated (n = 8) dogs lived a median of 7.5 days. Most dogs developed chemoresistance within weeks of initiating treatment, and consequently, survival times for AL remain disappointingly short.

Ulcerative colitis outpatient management: development and evaluation of tools to support primary care practitioners

BACKGROUND

Current models of care for ulcerative colitis (UC) across healthcare systems are inconsistent with a paucity of existing guidelines or supportive tools for outpatient management.

AIMS

This study aimed to produce and evaluate evidence-based outpatient management tools for UC to guide primary care practitioners and patients in clinical decision-making.

METHODS

Three tools were developed after identifying current gaps in the provision of healthcare services for patients with UC at a Clinical Insights Meeting in 2013. Draft designs were further refined through consultation and consolidation of feedback by the steering committee. Final drafts were developed following feasibility testing in three key stakeholder groups (gastroenterologists, general practitioners and patients) by questionnaire. The tools were officially launched into mainstream use in Australia in 2014.

RESULTS

Three quarters of all respondents liked the layout and content of each tool. Minimal safety concerns were aired and those, along with pieces of information that were felt to be omitted, that were reviewed by the steering committee and incorporated into the final documents. The majority (over 80%) of respondents felt that the tools would be useful and would improve outpatient management of UC.

CONCLUSION

Evidence-based outpatient clinical management tools for UC can be developed. The concept and end-product have been well received by all stakeholder groups. These tools should support non-specialist clinicians to optimise UC management and empower patients by facilitating them to safely self-manage and identify when medical support is needed.

Response to male odours in progestin receptor- and oestrogen receptor-containing cells in female rat brain

Sensory cues from male rats, such as odours and vaginal-cervical stimulation (VCS), play a modulatory role in female rat sexual behaviour. For example, exposure to male odours and VCS appears to be at least partially responsible for increases in sexual behaviour following repeated mating of oestradiol-primed female rats. Although there is evidence that VCS influences sexual behaviour via a ligand-independent progestin receptor (PR)-dependent mechanism, the mechanism by which odours influence sexual behaviour is not known. We tested the hypothesis that, similar to VCS, the effects of male odours on sexual behaviour are mediated by progestin receptors. Female rats were injected with the progestin antagonist, RU486, or oil vehicle and were then exposed to male-soiled bedding or clean bedding. Although exposure to male-soiled bedding resulted in higher levels of Fos immunoreactivity in brain areas associated with female sexual behaviour, the progestin antagonist did not reduce this effect. Furthermore, there was minimal coexpression of odour-induced Fos and progestin receptors in brain areas associated with female sexual behaviour. Together, these results suggest that the effects of male odours are not mediated by a PR-dependent mechanism. Therefore, we tested the hypothesis that oestrogen receptor (ER)-containing cells are involved in the effects of olfactory cues. Although there was virtually no coexpression of ERbeta and odour-induced Fos in brain areas associated with female sexual behaviour, exposure to male odours slightly increased the number of cells coexpressing ER(alpha) and odour-induced Fos in the posterodorsal medial amygdala. Although, these results do not support the hypothesis that the effects of odours are mediated by a PR-dependent mechanism, they suggest that integration of male odours and hormonal cues may occur in ER(alpha)-containing cells in the posterodorsal medial amygdala.

Sensory cues mediating mating-induced potentiation of sexual receptivity in female rats

Repeated mating of estradiol-primed female rats increases sexual receptivity. Two studies were conducted to determine the contribution of vaginal--cervical stimulation (VCS) to this increase. In the first study, female rats were repeatedly mated for 165 min. The vaginas of half of the females were covered with tape (masked) to prevent intromissions by the males. The remaining females were unmasked. Only females receiving intromissions (unmasked) showed a significant increase in sexual receptivity during repeated mating, suggesting that VCS from intromissions is necessary for repeated mating to increase sexual receptivity. In the second experiment, female rats received either experimentally administered VCS or control scapular stimulation administered with a plastic probe 1 h prior to testing for sexual receptivity. VCS applied in this manner significantly increased sexual receptivity. Together, these findings suggest that VCS from intromissions is one of the primary factors responsible for increases in sexual receptivity following repeated mating.

Androgen threshold to activate copulation differs in male rats prenatally exposed to alcohol, stress, or both factors

Few male rats prenatally exposed to a combination of alcohol and stress copulate spontaneously. This study determined adult sensitivity to testosterone (T) in males prenatally exposed to alcohol, to stress, or to both factors. Sexually naive males were tested with receptive females following castration and implantation of 20-, 30-, or 45-mm Silastic T-filled capsules. Serum T levels provided by these implants were measured. The behavior shown by males exposed only to prenatal alcohol did not differ from untreated control animals at any T dosage. Prenatal stress alone diminished the copulatory potential below control levels only when the intermediate T dosage was provided. Few males exposed to both alcohol and stress copulated under the lowest or the intermediate dose of adult T replacement, but most ejaculated normally when the largest capsule was implanted. The threshold to the sexual behavior-activating-properties of adult T exposure was moderately raised by prenatal stress but was severely affected when prenatal stress was combined with alcohol. We conclude that a diminished sensitivity to androgen in adulthood underlies some copulatory deficits resulting from treatments that alter fetal T levels. Such deficits may be concealed when behavior is evaluated in gonadally intact animals.

Elevation of bioactive transforming growth factor-beta in serum from patients with chronic fatigue syndrome

The level of bioactive transforming growth factor-beta (TGF-beta) was measured in serum from patients with chronic fatigue syndrome (CFS), healthy control subjects, and patients with major depression, systemic lupus erythematosis (SLE), and multiple sclerosis (MS) of both the relapsing/remitting (R/R) and the chronic progressive (CP) types. Patients with CFS had significantly higher levels of bioactive TGF-beta levels compared to the healthy control major depression, SLE, R/R MS, and CP MS groups (P < 0.01). Additionally, no significant differences were found between the healthy control subjects and any of the disease comparison groups. The current finding that TGF-beta is significantly elevated among patients with CFS supports the findings of two previous studies examining smaller numbers of CFS patients. In conclusion, TGF-beta levels were significantly higher in CFS patients compared to patients with various diseases known to be associated with immunologic abnormalities and/or pathologic fatigue. These findings raise interesting questions about the possible role of TGF-beta in the pathogenesis of CFS.

Somatomedin C (insulin-like growth factor I) levels in patients with chronic fatigue syndrome

Chronic fatigue syndrome is a disorder clinically quite similar to fibromyalgia syndrome, and it is of interest to examine if these two syndromes have pathogenetic as well as clinical features in common. Somatomedin C levels have been found to be lower in patients with fibromyalgia syndrome than in healthy controls. An attractive hypothesis relating sleep disturbance, altered somatotropic neuroendocrine function and fibromyalgia symptoms has been put forward as a plausible pathogenic mechanism for fibromyalgia syndrome. We therefore sought to investigate the level of somatomedin C in patients with chronic fatigue syndrome. Somatomedin C levels were determined by radioimmunoassay in frozen serum specimens from 49 patients with CFS and 30 healthy blood donor control subjects of similar age and gender. Somatomedin C levels were higher in patients with CFS than in healthy control subjects (255.3 +/- 68.5 vs 211.9 +/- 76.2, P = 0.01). There was no effect of gender, use of nonsteroidal anti-inflammatory drugs or tricyclic drugs on levels of somatomedin C. There was a tendency for somatomedin C levels to fall with age. In contrast to patients with fibromyalgia, in whom levels of somatomedin C have been found to be reduced, levels in patients with CFS were found to be elevated. Thus, despite the clinical similarities between these two conditions, they may be associated with different abnormalities of sleep and/or of the somatotropic neuroendocrine axis.

Immunoglobulin subclass levels in chronic fatigue syndrome

The levels of immunoglobulin subclasses were determined for 46 patients meeting the original Centers for Disease Control case definition of chronic fatigue syndrome and were compared to values obtained for 50 age- and gender-matched healthy volunteer blood donor controls. The levels of immunoglobulin subclasses in these groups were further compared to a third group of additional chronic fatigue syndrome cases from whom samples had been obtained and frozen prospectively over a period of 7 years. These data do not demonstrate significant immunoglobulin subclass deficiencies in patients with chronic fatigue syndrome.

Acquisition of antigens characteristic of adult pericentral hepatocytes by differentiating fetal hepatoblasts in vitro

Antigens specific to pericentral hepatocytes have been studied in adult mouse liver, during fetal development, and in cultured fetal hepatoblasts. Antibody reactive with glutamine synthetase stained all fetal liver cells but almost all cells lost this antigen after birth; only a single layer of pericentral cells retained it in adulthood. In contrast, monoclonal antibodies to major urinary protein (MUP) did not detect the antigen until approximately 3 wk after birth, after which time the cells within 6-10 cell diameters of the central veins were positive. Cultured fetal liver cells from embryos at 13 +/- 1 d of gestation were capable of differentiating in vitro to mimic events that would occur had the cells remained in the animal. About 10-20% of the explanted cells grew into clusters of hepatocyte-like cells, all of which stained with albumin antibodies. MUP monoclonals were reactive with one-half of the differentiated fetal hepatocytes. Glutamine synthetase was present in all hepatocytes after several days in culture and gradually decreased and remained in only occasional cells, all of which also contained the MUP antigen. These findings suggest that a sequence of gene controls characterizes expression of specific genes in developing liver, and that differentiating fetal hepatoblasts are capable of undergoing similar patterns of gene activity in culture.

Factors that interact with the rat albumin promoter are present both in hepatocytes and other cell types

The rat albumin promoter inserted in adenovirus directs transcription in human and rodent hepatoma cells and in rodent hepatocytes (Friedman et al. 1986) and Babiss et al. (1986) but not in HeLa cells or myeloma cells. The nucleotides between -43 and -156 of the RNA start site of the rat albumin gene are required for this cell-specific expression. Protein binding studies (footprints, exonuclease III stops, and gel shifts) all indicate specific interaction in the -80 to -130 region of the gene with factors present in nuclear extracts of hepatocytes and hepatomas, but also from extracts of other cells that do not express the albumin gene. To observe albumin promoter binding, a smaller amount of extract of liver cell nuclei was required compared to extracts of HeLa cell or kidney cell nuclei. In addition, the various tests of DNA-protein interaction did not give qualitatively identical results with extracts from different cells. However, it seems clear that factors are present in several cell types where albumin genes are inactive that will bind to those DNA sequences demonstrated to be necessary for cell-specific expression of this gene. These factors could either be similar but nonidentical factors or the same factors that are modified differently in different cell types.

Morbidity and mortality of coronary bypass grafting in patients 70 years of age and older

The hospital mortality and major factors contributing to hospital morbidity and postoperative length of stay were examined in 597 consecutive patients 70 years of age and older who underwent isolated coronary artery bypass grafting (CABG) between January, 1978, and December, 1983. The mean age of the patients was 73 years, and 66% were men. Unstable angina was present in 59% of patients, left main coronary disease in 13%, and moderate or severe left ventricular dysfunction in 10%. The mean number of arteries grafted per patient was 3.4. The hospital mortality was 2.7% (16 patients) and was higher than the mortality among 4,125 patients less than 70 years of age (0.4% in 18 patients) operated on during the same interval (p less than 0.001). In multivariate regression analyses, age of 80 years or greater, evolving myocardial infarction, serious coexisting illness, major left ventricular dysfunction, emergent operation, and the development of major postoperative complications were significant (p less than 0.05) independent predictors of increased hospital mortality. Major complications occurred in 135 patients (23%). In multivariate analyses, the presence of vascular disease, serious concomitant illness, and the need for urgent or emergent operation were significant independent predictors of the development of major postoperative complications. The mean duration of postoperative hospital stay was 10.6 +/- 6 (standard deviation) days. In multivariate analyses, the development of major postoperative complications was the only variable independently predictive of prolonged hospital stay. With current techniques, CABG procedures can be safely performed in the elderly with mortality and morbidity rates only slightly higher than those in younger patients.(ABSTRACT TRUNCATED AT 250 WORDS)