Acquired systemic tolerance to rat cardiac allografts induced by intrathymic inoculation of synthetic polymorphic MHC class I allopeptides

This study extends the finding that intrathymic (IT) injection of 3M KC1 extracts of T cells induces transplant tolerance to the use of well defined polymorphic MHC class I allopeptides derived from the hypervariable domain of RT1.Au (WF MHC class I). While three of the six synthetic RT1.Au peptides were immunogenic, three others were nonimmunogenic when tested in ACI responders. In our initial studies, we examined the effects of IT injection of a mixture of equal concentrations of the three nonimmunogenic RT1.Au peptides on WF cardiac allograft survival in ACI recipients. The results showed that a single IT injection of 100 and 300 microg class I MHC allopeptides on day -7 relative to cardiac transplant did not significantly prolong graft survival in naive ACI recipients (MST of 9.8, and 12.3 days vs. 10.5 days in controls). In contrast, 600 microg allopeptides injected IT resulted in modest prolongation of graft to an MST of 19.5 days. However, IT injection of 600 microg allopeptides combined with 0.5 ml ALS on day -7 led to permanent acceptance (>200 days) of cardiac allografts in 7/9 ACI recipients compared with survival of 24.2 days in ALS alone treated controls. In contrast, similar treatment led to acute rejection of third party (Lewis) cardiac allografts. Intravenous injection of 600 microg allopeptides combined with ALS did not result in prolonged graft survival (26.8 days). The long-term unresponsive ACI recipients (>100 days) challenged with second-set cardiac grafts accepted permanently donor-type (WF) grafts while rejecting the third party (Lewis) grafts, a finding that confirms acquired systemic tolerance. These findings confirm the role of IT injection of synthetic polymorphic allopeptides in the induction of acquired thymic tolerance and provide the rationale for testing this strategy in large animals and eventually in man.

Pilocarpine gel for the treatment of demodicosis--a case series

BACKGROUND

Excessive numbers of the mite, Demodax folliculorum, in the eyelash follicies cause itching and is referred to as demodicosis. We evaluated 4% pilocarpine gel as a treatment for this condition.

METHODS

An advertisement was placed in a retirement home newsletter, requesting persons with ocular discomfort. Respondents were examined for Demodex and persons with abundant mites were invited to participate. One eye was treated with pilocarpine gel; the other eye was untreated. The relative abundance of mites was evaluated at baseline, after 1 and 2 weeks of treatment. Subjects kept a daily log of symptoms.

RESULTS

Eleven of 22 persons with ocular itching had abundant Demodax. Mites were reduced significantly by the treatment (p = 0.017). The amount of mite reduction was closely correlated with the extent to which itching was alleviated (r = 0.811, p = 0.008).

CONCLUSION

Abundant Demodex is an important cause of ocular itching in older persons. Mites can be reduced with pilocarpine gel and itching alleviated.

Evidence for a schizophrenia vulnerability locus on chromosome 8p in the Irish Study of High-Density Schizophrenia Families

OBJECTIVE

This study was an attempt to replicate evidence for a vulnerability locus for schizophrenia and associated disorders in the 8p22-21 region reported by Pulver and colleagues.

METHOD

The linkage sample of the Irish Study of High-Density Schizophrenia Families consists of 265 multiplex families containing 1,408 individuals. Fifteen markers covering 30 centimorgans on chromosome 8p were tested. Three statistical methods were used: two-point and multipoint heterogeneity lod scores and a multipoint nonparametric test.

RESULTS

According to two-point heterogeneity lod scores, the strongest evidence for linkage was found for markers D8S1731 (maximum lod score = 2.00), D8S1715 (maximum lod score = 2.52), and D8S133 (maximum lod score = 2.08) by assuming a phenotypic definition of all psychiatric illness and a range of genetic models. According to multipoint heterogeneity lod scores, the strongest evidence for linkage (maximum lod score = 2.34), found by using a dominant genetic model and a broad definition of the schizophrenia spectrum, extended over a 10-cM region between markers D8S1715 and D8S1739. Multipoint nonparametric linkage found the strongest evidence (maximum z = 2.51) over a broader region when either a diagnosis of core schizophrenia or a narrow definition of the schizophrenia spectrum was used. This putative vulnerability locus was segregating in 10%-25% of the families studied.

CONCLUSIONS

This study supports the existence of a vulnerability locus for schizophrenia on chromosome 8p. In this sample, this locus appears to influence the risk of illness in only a modest proportion of families and predisposes to a range of schizophrenia spectrum and possibly nonspectrum disorders.

Patient-initiated prevention discussions. Two interventions to stimulate patients to initiate prevention discussions

BACKGROUND

When patients are active participants in discussions, comprehension and compliance are likely to improve. This study examines the use of two interventions to aid patients in initiating such discussions in the area of health maintenance.

METHODS

The study was a randomized controlled trial of adult patients. The first intervention used two cards that listed seven core health maintenance concerns. The second intervention used a brief session with a nurse to help patients identify their health risks and develop a plan for seeking any desired information about these risks. An exit questionnaire and a telephone interview 4 to 6 weeks later assessed the extent to which (1) information seeking by patients was stimulated; (2) patients recalled the information obtained; (3) patients used the information to effect lifestyle changes; and (4) patients felt they participated in the decision to discuss health maintenance.

RESULTS

Both interventions stimulated patients to request health maintenance information (both P < .05); the second intervention significantly increased patient recall (P = .018). Neither intervention, however, had a significant impact on lifestyle change or sense of participation in the decision to initiate discussion. Analysis of the second intervention did show that both increasing patients' recall of information (P = .008) and sense of involvement in the decision to discuss health maintenance (P = .003) significantly increases the likelihood of lifestyle change.

CONCLUSIONS

Two interventions have been developed that are relatively simple and inexpensive methods to stimulate patients to seek health maintenance, and quite probably other health-related information. The blunted impact of these two interventions, however, raises the question of whether such simple and relatively inexpensive interventions are strong enough to stimulate patients to use this information to initiate change when one seeks to address a wide range of risks.

Mechanisms of indirect allorecognition in graft rejection: class II MHC allopeptide-specific T cell clones transfer delayed-type hypersensitivity responses in vivo

Recent animal studies suggest that indirect T-cell recognition of alloantigen plays an important role in allograft rejection and tolerance. In this study, we generated T cell clones from Lewis (LEW, RT1(l)) rat lymph node cells that had been primed in vivo by immunization with immunogenic class II MHC allopeptide RT1.D(u)beta2, representing residues 20-44 of the polymorphic beta chain of RT1.Dbeta(u) (Wistar Furth [WF]). Using reverse transcriptase polymerase chain reaction transcript analysis with specific rat T cell receptor Vbeta primers, we show that six out of nine T cell clones specifically proliferated to RT1.D(u)beta2 and expressed Vbeta 9. One of these clones, clone 2F4, which specifically proliferated to RT1.D(u)beta2 in a dose-response fashion and produced interferon-gamma in response to restimulation by RT1.D(u)beta2, was selected for further studies. The beta-chains of RT1.D(l) and RT1.D(u) residues 20-44 differ by two amino acids at positions 30 and 38. We synthesized two peptides, each containing a single polymorphic site: RT1.D(u)beta 20-33 and RT1.D(u)beta 31-44. Both these peptides were immunogenic by LEW responders, since lymph node cells primed by immunization proliferated equally to the peptides in vitro. Interestingly, in vitro dose-response studies with clone 2F4 showed better proliferative response to peptide RT1.D(u)beta 20-33 than to peptide RT1.D(u)beta 31-44, indicating that this T cell clone preferentially recognizes a single amino acid difference on residue 30. Finally, it has been suggested that indirect allorecognition by CD4+ T cells mediate graft rejection by delayed-type hypersensitivity responses, although definitive studies are lacking. Systemic injection of the 2F4 clone to naive LEW rats elicited an antigen-specific delayed-type hypersensitivity response against RT1.D(u)beta2 peptide and WF splenocytes, confirming indirect presentation in vivo. These data demonstrate that Th1 cell clones generated by in vivo priming via the indirect pathway utilize specific T cell receptor Vbeta and recognize single amino acid differences in the allopeptide. More importantly,these Th1 clones are capable of mediating a specific immune response in vivo. These studies with MHC allopeptide-specific T cell clones further delineate the cellular mechanisms of indirect allorecognition and provide a potential strategy to study its role in acute and chronic rejection, and tolerance.

Paclitaxel plus carboplatin in advanced non-small-cell lung cancer: a phase II trial

PURPOSE

Studies conducted by the Eastern Cooperative Oncology Group (ECOG) indicate both paclitaxel and carboplatin are associated with an improvement in 1-year survival in patients with stage IV non-small-cell lung cancer (NSCLC). Based on these findings, a phase II trial of these agents in combination was conducted in patients with advanced NSCLC.

PATIENTS AND METHODS

Eligibility included previously untreated stage IIIB or IV NSCLC patients with a good performance status (PS). Paclitaxel (135 or 175 mg/m2) was administered by 24-hour infusion on day 1, followed by a 1-hour infusion of carboplatin on day 2 (300 mg/m2 or dosed to an area under the concentration-time curve [AUC] of 6 mg/mL.min). Treatment was repeated every 28 days for a total of six cycles. Hematopoietic growth factors were not routinely used.

RESULTS

Among 51 eligible patients, there were no complete and 14 partial responses, for an overall response rate of 27% (95% confidence interval [CI], 17% to 41%). The median progression-free survival time was 23.8 weeks (range, 12.1 to 73.9) and median survival time, 38 weeks. The survival rate at 1 year was 32%. Grade 3 or 4 granulocytopenia and thrombocytopenia were observed in 47% and 3%, respectively, of the 184 treatment cycles administered. The most common nonhematologic toxicities included nausea and emesis, neuropathy, and arthralgia/myalgia.

CONCLUSION

Paclitaxel plus carboplatin is a moderately active regimen in patients with advanced NSCLC and warrants comparison with existing cisplatin-based regimens in a prospective randomized trial. The toxicities of this regimen are well tolerated in patients with a good PS.

Immunomodulatory function of major histocompatibility complex-derived peptides

Recent advances with regard to the structure and function of the major histocompatibility molecules have given rise to a better understanding of T cell receptor interaction with the major histocompatibility complex plus peptide complex on the surface of antigen-presenting cells, and have highlighted the pivotal role of the peptide in determining the subsequent T cell response. There has therefore been increased interest in the use of synthetic peptides to alter T cell responses to foreign antigens. The purpose of this review is to highlight the recent studies which demonstrate the potential immunomodulatory functions of peptides derived from major histocompatibility complex molecules.

T cell recognition of xeno-MHC peptides during concordant xenograft rejection

T cell recognition of xenoantigens is likely to play a key role in rejection of xenografts surviving hyperacute and delayed xenograft rejection, but the mechanisms of how this might occur are unknown. We used synthetic rat class II MHC peptides to study the role of the indirect pathway, where processed xenogeneic MHC antigens are presented in the context of self MHC, in a concordant xenograft rejection model in vivo. Mice of four different strains, BALB/c, B1O.A, CBA/ca, and C57BL/6j, were immunized with a mixture of rat class II MHC 25-mer xenopeptides representing the full-length sequence of the beta chain hypervariable domain of either RT1.Du (DR and I-E like) or RT1.Bu (DQ and I-A like) of the Wistar-Furth (WF) (RT1u) rat. Draining lymph node cells were capable of recognizing and proliferating to specific class II xeno-MHC peptides. The immunogenicity of the different peptides varied with the responder mouse strain. Responder T cells were CD4+, and were inhibited by anti-I-A and anti-I-E antibodies. We then examined the proliferative response of T cells from B1O.A primed by WF skin or vascularized cardiac xenografts to the class II MHC xenopeptides, when presented by naive B1O.A splenic antigen-presenting cells. These T cells were capable of proliferating to the same xeno-MHC peptides shown to be immunogenic by immunization. These data confirm the occurrence of self-restricted T cell recognition of xeno-MHC peptides in xenograft rejection, and provide the rationale for further investigating the role of the indirect pathway of recognition in xenotransplantation.

Irish study on high-density schizophrenia families: field methods and power to detect linkage

Large samples of multiplex pedigrees will probably be needed to detect susceptibility loci for schizophrenia by linkage analysis. Standardized ascertainment of such pedigrees from culturally and ethnically homogeneous populations may improve the probability of detection and replication of linkage. The Irish Study of High-Density Schizophrenia Families (ISHDSF) was formed from standardized ascertainment of multiplex schizophrenia families in 39 psychiatric facilities covering over 90% of the population in Ireland and Northern Ireland. We here describe a phenotypic sample and a subset thereof, the linkage sample. Individuals were included in the phenotypic sample if adequate diagnostic information, based on personal interview and/or hospital record, was available. Only individuals with available DNA were included in the linkage sample. Inclusion of a pedigree into the phenotypic sample required at least two first, second, or third degree relatives with non-affective psychosis (NAP), one whom had schizophrenia (S) or poor-outcome schizo-affective disorder (PO-SAD). Entry into the linkage sample required DNA samples on at least two individuals with NAP, of whom at least one had S or PO-SAD. Affection was defined by narrow, intermediate, and broad criteria. The phenotypic sample contained 277 pedigrees and 1,770 individuals and the linkage sample 265 pedigrees and 1,408 individuals. Using the intermediate definition of affection, the phenotypic sample contained 837 affected individuals and 526 affected sibling pairs. Parallel figures for the linkage sample were 700 and 420. Individuals with schizophrenia from these multiplex pedigrees resembled epidemiologically sampled cases with respect to age at onset, gender distribution, and most clinical symptoms, although they were more thought-disordered and had a poorer outcome. Power analyses based on the model of linkage heterogeneity indicated that the ISHDSF should be able to detect a major locus that influences susceptibility to schizophrenia in as few as 20% of families. Compared to first-degree relatives of epidemiologically sampled schizophrenic probands, first-degree relatives of schizophrenic members from the ISHDSF had a similar risk for schizotypal personality disorder, affective illness, alcoholism, and anxiety disorder. With sufficient resources, large-scale ascertainment of multiplex schizophrenia pedigrees is feasible, especially in countries with catchmented psychiatric care and stable populations. Although somewhat more severely ill, schizophrenic members of such pedigrees appear to clinically resemble typical schizophrenic patients. Our ascertainment process for multiplex schizophrenia families did not select for excess familial risk for affective illness or alcoholism. With its large sample ascertained in a standardized manner from a relatively homogeneous population, the ISHDSF provides considerable power to detect susceptibility loci for schizophrenia.

Can prostate-specific antigen be used as a valid end point to determine the efficacy of chemotherapy for advanced prostate cancer?

It is current practice in many clinical trials evaluating new chemotherapy regimens for the treatment of advanced prostate cancer to use prostate-specific antigen (PSA) decline as a response criteria with the assumption that the level of PSA reflects the efficacy of chemotherapy. Advanced prostate cancer is heterogeneous; therefore, the validity of PSA decline as a measurable end point was studied in advanced human prostate-cancer cell lines: androgen-sensitive LNCaP and androgen-insensitive PC3 cells. Each cell line was grown for 4 days with escalating doses of Adriamycin or vinblastine. Cell counts, intracellular PSA concentrations, and secreted PSA levels were determined daily for 4 days. Untreated LNCaP cells had constant secretion of PSA per cell. In contrast, LNCaP cells treated with Adriamycin or vinblastine had an 80% reduction in cell numbers and a 3-fold increase in secreted PSA per cell by day 4. In contrast, PC3 cells had a different response to Adriamycin and vinblastine. Both drugs reduced cell numbers by 97% of control values and suppressed PSA production in the remaining viable cells by 4 days in culture. Thus, prostate-cancer cell production of PSA is variable with chemotherapy and the PSA level may not accurately reflect the actual tumor response to chemotherapy.

Low-density lipoprotein particle size distribution in end-stage renal disease treated with hemodialysis or peritoneal dialysis

Dyslipidemia accompanies end-stage renal disease (ESRD) and contributes to the high incidence of cardiovascular disease in patients on chronic dialysis treatment. The lipid abnormalities of elevated triglyceride level and reduced high-density lipoprotein cholesterol level that occur in ESRD are associated in the normal population with an altered distribution of low-density lipoprotein (LDL) particle size, a pattern associated with increased risk of coronary heart disease. To assess the effect of ESRD on LDL particle size distribution, we examined plasma lipid levels and LDL particle size in 43 subjects on chronic hemodialysis, 23 subjects on continuous ambulatory peritoneal dialysis, and 30 control subjects with normal renal function. Of subjects on continuous ambulatory peritoneal dialysis, 48% had small LDL particle size compared with 23% of subjects on hemodialysis and 7% of control subjects. Subjects on both forms of dialysis also had higher triglyceride levels and lower high-density lipoprotein cholesterol levels that correlated with LDL particle size. We conclude that altered LDL particle size forms an important component of the metabolic abnormalities that contribute to the increased cardiovascular risk found in ESRD.

A potential vulnerability locus for schizophrenia on chromosome 6p24-22: evidence for genetic heterogeneity

In 265 Irish pedigrees, with linkage analysis we find evidence for a vulnerability locus for schizophrenia in region 6p24-22. The greatest lod score, assuming locus heterogeneity, is 3.51 (P = 0.0002) with D6S296. Another test, the C test, also supported linkage, the strongest results being obtained with D6S296 (P = 0.00001), D6S274 (P = 0.004) and D6S285 (P = 0.006). Non-parametric analysis yielded suggestive, but substantially weaker, findings. This locus appears to influence the vulnerability to schizophrenia in roughly 15 to 30% of our pedigrees. Evidence for linkage was maximal using an intermediate phenotypic definition and declined when this definition was narrowed or was broadened to include other psychiatric disorders.

The role of emotionality and regulation in children's social functioning: a longitudinal study

Multiple measures of children's emotionality (emotional intensity and negative affectivity), regulation (including attentional and behavioral regulation and coping), and social functioning (teachers' reports of nonaggressive/socially appropriate behavior and prosocial/socially competent behavior; and parents' reports of problem behavior) were obtained for 6-8-year-olds. In addition, emotionality, attentional regulation, and coping were assessed 2 years previously. Social functioning was expected to be predicted by low negative emotionality and high levels of regulation. In general, the data supported the predictions, although the findings for parent reports of problem behavior were primarily for boys. Prediction of social functioning from measures of regulation and emotionality occurred primarily within a given context (school vs. home) rather than across contexts, even though there were relations across reporters within the school or home context. In addition, vagal tone, a marker of physiological regulation, was positively related to competent social functioning and emotionality/regulation for boys, but inversely related for girls.

Prosocial development in late adolescence: a longitudinal study

Change in prosocial moral reasoning over 15 years, gender differences in prosocial reasoning, and the interrelations of moral reasoning, prosocial behavior, and empathy-related emotional responses were examined with longitudinal data from 17-18- and 19-20-year-olds and data from adolescents interviewed for the first time. Hedonistic reasoning declined in use until adolescence, and then increased somewhat in early adulthood. Needs-oriented and stereotypic reasoning increased until mid-childhood or early adolescence and then declined in use. Direct reciprocity and approval reasoning, which appeared to be on the decline in mid-adolescence in previous follow-ups, showed no decline into early adulthood. Several modes of higher-level reasoning increased in use across adolescence and early adulthood. Females' overall reasoning was higher than males'. Scores on interview and objective measures of prosocial moral reasoning were positively correlated. Consistent with expectations, there was some evidence of relations among prosocial reasoning, prosocial behavior, sympathy, and perspective taking.

Culture methods for the detection of minimal tumor contamination of hematopoietic harvests: a review

The evaluation of minimal residual disease in patients and hematopoietic cell grafts is of considerable importance for staging disease, determining the response to treatment, and monitoring the efficiency of ex vivo purging or positive selection procedures. The most widely used techniques are immunocytochemical staining and the polymerase chain reaction; however, these assays do not measure the viability or clonogenic capacity of the detected cells. For this purpose, a culture technique must be used. This paper reviews the status, advantages, and limitations of this approach and the detection of tumor cells in bone marrow and peripheral blood.

Information for family carers: does it help?

Family carers in Victoria were identified through a statewide telephone survey in 1993. A total of 976 carers was interviewed and a random sample of approximately one in 10 (n = 103) were offered the Carer Support Kit leaflet. The leaflet details the components of the Carer Support Kit (a Federal Government initiative developed in 1992-93) and informs carers how to apply for it through the Victorian Carers' Association. Approximately three-quarters of these carers accepted the offer, and around a third subsequently applied for the kit. Carers who applied for the kit reported significantly more overload and lower life satisfaction than those who did not apply. Only two-thirds of those mailed the kit (just 23 per cent of the eligible study sample) went on to use it. Those who had not used it reported significantly more negative emotions and health problems than those who used it, suggesting that stress and crises could preclude utilisation of the information. A brief evaluation of the components of the kit is presented; however, findings need to be treated with caution in view of the small sample size.

The indirect pathway of allorecognition. The occurrence of self-restricted T cell recognition of allo-MHC peptides early in acute renal allograft rejection and its inhibition by conventional immunosuppression

There is evidence that T cells can "directly" recognize intact allo-MHC molecules on the surface of allogeneic stimulator or target cells, and/or "indirectly" recognize processed allo-MHC peptides presented by self antigen-presenting cells (APCs). We and others have recently demonstrated that in vivo-primed rat CD4+ T cells recognize and proliferate to specific polymorphic amino acid sequences when presented as MHC allopeptides by self APCs. Studies on the mechanisms of indirect T cell recognition of alloantigen are now reported. First, we studied the immunogenicity of 4 synthetic polymorphic class II MHC allopeptides representing full-length sequences of the hypervariable domains of RT1.Du beta (DR or I-E-like) in several responder strains: LEW (RT1(l)), ACI (RT1a), BUF (RT1b), BN (RT1n), and control syngeneic WF (RT1u) strains. Immunogenicity of the individual 25mer allopeptides varied in the different responder strains, indicating that self-restricted T cell recognition of allo-MHC peptides is determined not only by polymorphisms, but also by the responder MHC genotype. Self-restricted CD4+ T cell recognition of processed allo-MHC peptides has been shown to occur during acute skin and cardiac allograft rejection, and there is evidence that this pathway may play an important role in initiating and amplifying the immune response to allografts. T cells from LEW animals primed in vivo by WF (RT1u) vascularized renal allografts were capable of proliferating to the RT1.Du beta peptides as early as 3 days postengraftment, when presented by self APCs. We then tested the effects of various immunosuppressive drugs on self-restricted primed T cell proliferative response to an immunogenic MHC allopeptide in vitro. Methylprednisolone, cyclosporine, and FK506 inhibited the proliferative response of RT1.Du beta 2-primed LEW T cells in a dose-dependent fashion. In addition, a single injection of cyclosporine (25 mg/kg i.m.) to LEW recipients of WF renal allografts on the day of transplantation completely abolished the proliferative response of in vivo-primed T cells to RT1.Du beta 2, indicating the susceptibility of the indirect pathway of allorecognition to conventional immunosuppressive drugs.

A phase I trial of intrahepatic verapamil and doxorubicin. Regional therapy to overcome multidrug resistance

BACKGROUND

Verapamil can modulate multidrug resistance in vitro, but only at levels that are not tolerable when administered systemically. Regional strategies of drug administration may permit the delivery of high concentrations of a drug to specific areas with lower systemic levels. Colorectal cancers typically express the multidrug resistance phenotype.

METHODS

A Phase I trial was performed to determine the maximum tolerable dose (MTD) and dose limiting toxicities of verapamil by hepatic artery infusion, together with doxorubicin, to patients with hepatic metastases of colorectal cancer. Fourteen patients with metastatic colorectal cancer received a 14-hour intrahepatic infusion of verapamil. Six hours after the start of the infusion, a fixed dose of doxorubicin (50 mg/m2) was given, also via the hepatic artery, over a 30-minute period. Patients were followed by cardiac telemetry but were not in an intensive care setting, and no invasive monitoring was used. All patients had received prior intrahepatic chemotherapy.

RESULTS

The MTD of intrahepatic verapamil on this schedule in this patient population was 1.2 mg/kg/hour. Hypotension was the dose limiting toxicity. No major objective responses were noted in this heavily pretreated patient population. A dose of 1.0 mg/kg/hour is recommended for Phase II trials.

CONCLUSIONS

Based on estimations of normal hepatic artery blood flow, the estimated concentration of verapamil delivered to the hepatic tumors at 1.0 mg/kg/hour is 3.6 micrograms/ml (7.3 microM), which is comparable to concentrations at which an in vitro reversal of MDR is seen. This study demonstrates that the systemic toxicities of an MDR reversal agent can be overcome by regional drug delivery, establishing this approach as an important model system for further study of MDR modulation.

The response of human dermal microvascular endothelial cells to hypoxia

Dermal microvascular endothelial cells (DMEC) exposed to hypoxic conditions show a rapid induction of several proteins that do not increase in other cell types placed in a similar environment. These DMEC proteins differ from the well-characterized stress proteins that have been observed in a wide variety of cultured cell types. The DMEC proteins are induced rapidly, within 2-4 h, and are expressed transiently. They include a group of acidic proteins (pI approximately 5-5.2) with molecular weights in the range 100,000-120,000 and at least one glycoprotein (pI 5.1, M(r) 57,000) that is probably expressed on the cell surface. In some primary DMEC cell strains, this response is accompanied by a transient overall increase in protein synthesis. The oxygen-regulated proteins (ORP) that are induced in most other cell types under hypoxic conditions show little variation in their rate of synthesis in DMEC within the first 24 h. The response of DMEC differs from that of umbilical vein endothelial cells (UVEC) and from spindle-shaped cells derived from DMEC, that show a response to hypoxia that is similar to most other cell types. The changes seen in DMEC proteins take place in the same time scale as ischemia-reperfusion injury and may reflect the specialized change of functions of the microvasculature observed under conditions of hypoxic stress in vivo.