Evidence of reciprocity of bcl-2 and p53 expression in human colorectal adenomas and carcinomas

Evidence of accumulating for the failure of apoptosis as an important factor in the evolution of colorectal cancer and its poor response to adjuvant therapy. The proto-oncogene bcl-2 suppresses apoptosis. Its expression could provide an important survival advantage permitting the development of colorectal cancer. The expression of bcl-2 and p53 was determined by immunohistochemistry in 47 samples of histologically normal colonic mucosa, 19 adenomas and 53 adenocarcinomas. Expression of bcl-2 in colonic crypts > 5 cm from the tumours was confined to crypt bases but was more extensive and intense in normal crypts < 5 mm from cancers. A higher proportion of adenomas (63.2%) than carcinomas (36.5%) expressed bcl-2 (P < 0.05). A lower proportion of adenomas (31.6%) than carcinomas (62.3%) expressed p53 (P < 0.02). A total of 26.3% of adenomas and 22% of carcinomas expressed both bcl-2 and p53. To determine whether these samples contained cells which expressed both proteins, a dual staining technique for bcl-2 and p53 was used. Only 1/19 adenomas and 2/53 carcinomas contained cells immunopositive for both bcl-2 and p53. Moreover there was evidence of reciprocity of expression of bcl-2 and p53 in these three double staining neoplasms. We suggest that bcl-2 provides a survival advantage in the proliferative compartment of normal crypts and colorectal neoplasms. However, its expression is lost during the evolution from adenoma to carcinoma, whereas p53 expression is increased, an event generally coincident with the expression of stabilised p53, which we presume to represent the mutant form.

Characterization of cell volume loss in CEM-C7A cells during dexamethasone-induced apoptosis

A reduction in cell volume is a fundamental feature of apoptosis. We have characterized changes in cell volume, together with nuclear changes, occurring in dexamethasone-induced apoptosis in CEM-C7A lymphoblastoid cells. Cell volume was measured by electronic cell sizing and flow cytometry, and two distinct phases of volume loss were observed. The first phase began 12 h after addition of dexamethasone (5 microM) and progressed until 36 h when chromatin condensation was detected in intact cells. Removal of dexamethasone before 36 h (the precommitment period) resulted in reversal of the volume decrease and prevented the appearance of nuclear changes. Cell shrinkage in the first 24 h of dexamethasone exposure was associated with a net loss of potassium but no change in cellular buoyant density. There were no significant differences in the rates of volume recovery after either hypertonic or hypotonic stimuli. These observations favor a mechanism of cell shrinkage involving loss of the entire cytoplasmic contents, possibly following proteolysis, rather than loss of only osmolytes and water. The second phase of volume loss was coincident with chromatin condensation and was associated with cellular fragmentation and a reduction in cellular density. We conclude that volume loss in this model of apoptosis is mediated by multiple mechanisms that are both dependent and independent of cellular fragmentation.

Expression of insulin-like growth factors in two bovine oviductal cultures employed for embryo co-culture

We have investigated the patterns of expression and cellular localization of polypeptides and mRNAs encoding IGF-I and IGF-II in intact bovine oviduct and two bovine oviductal primary cultures (monolayers and vesicles) which are utilized for supporting development in vitro. IGF-I and IGF-II polypeptides were localized by immunocytochemistry in intact oviduct and in both primary cultures for an 8-day culture interval, but IGF-II polypeptide displayed a more restricted distribution in day 8 monolayer cultures. IGF-I and IGF-II mRNAs were localized in both oviductal cell cultures as assessed by in situ hybridization. We were unable to detect IGF-I and IGF-II mRNAs in intact oviduct by in situ hybridization; however, transcripts encoding IGF-I and IGF-II mRNAs were detected in intact oviduct cell preparations and all primary culture samples by reverse transcription-PCR methods. The origin and phenotypic stability of these cultures was assessed by immunostaining with antibodies raised against vimentin (mesenchymal cell marker) and cytokeratin (epithelial cell marker). Over the culture period, the proportion of vimentin-immunoreactive cells increased in the monolayer cultures but remained at a low level in the vesicle cultures which were predominantly composed of cytokeratin-positive cells. The results suggest that oviductal cell co-culture may facilitate early mammalian development, in part, by the establishment of paracrine growth factor circuits.

Apoptosis and gastrointestinal pharmacology

Apoptosis is a fundamental biological process that regulates cell number and removes cells that are neoplastic or infected by viruses. This review summarises present knowledge of the mechanisms and genetic regulation of apoptosis in the gastrointestinal tract and highlights areas of pharmacological relevance. In the intestine, apoptosis occurs in the crypt and possibly at the villus tip. Abnormal apoptosis plays a role in a number of gastrointestinal disease including colorectal cancer. The effects of cytotoxic drugs, chemical carcinogens, nonsteroidal anti-inflammatory drugs, short-chain fatty acids, bile salts and anthraquinolones on apoptosis in the gastrointestinal tract are reviewed.

O6-alkylguanine-DNA alkyltransferase attenuates triazene-induced cytotoxicity and tumor cell immunogenicity in murine L1210 leukemia

Methylating and chloroethylating triazene compounds (TZCs) are effective antitumor agents in murine leukemias and can induce the appearance of novel antigens in leukemic cells (chemical xenogenization). Recently, it has been shown that TZCs might have a role in the treatment of patients affected by acute myelogenous leukemias that express low levels of the DNA repair enzyme, O6-alkylguanine-DNA alkyltransferase (OGAT). In this report, we have evaluated the role of this DNA repair enzyme in the leukemic cell response to the xenogenizing and cytotoxic properties of TZCs. OGAT-deficient murine leukemic L1210 cells were transfected with a recombinant ecotropic retrovirus containing the coding region for the human OGAT protein. Selected clones expressed the human OGAT transcript and had greatly increased OGAT activity. Compared to OGAT-deficient cells, OGAT-expressing cells were considerably more resistant to the xenogenizing properties of 1-(p-chlorophenyl)-3,3- dimethyl-triazene, measured in terms of leukemia graft rejection, and were less susceptible to the cytotoxic activity of the TZCs 8-carbamoyl-3-methyl-imidazo [5,1-d]-1,2,3,5-tetrazin-4(3H)-one and 8-carbamoyl-3-(2-chloroethyl)imidazo [5,1-d]-1,2,3,5-tetrazin-4(3H)-one. These data suggest that methylation of the O6 position of guanine is involved in the appearance of increased tumor immunogenicity after exposure to methylating TZC and that OGAT is able, at least in part, to counteract the cytotoxic effects of methylating and chloroethylating agents.

Expression of genes encoding antioxidant enzymes in preimplantation mouse and cow embryos and primary bovine oviduct cultures employed for embryo coculture

Preimplantation embryos from a variety of mammalian species contrast markedly in their response to culture in vitro. Murine preimplantation embryos display a wider tolerance than other mammalian species to culture environments, and this has contributed to the development of several effective defined culture media. Embryo coculture on somatic cells remains the most effective method of supporting reasonable rates of bovine preimplantation development in vitro. The patterns of gene expression for several antioxidant enzymes during preimplantation murine and bovine development were examined by use of the reverse transcription-polymerase chain reaction technique to determine whether the differential developmental capacity of mammalian preimplantation embryos in culture may reflect variations in the patterns of expression for a series of antioxidant enzymes. Transcripts for catalase, CuZn-containing superoxide dismutase (CuZn-SOD), Mn-SOD, glutathione peroxidase (GPX), and glutamylcysteine synthetase (GCS) were detected in mouse embryos at all stages of development regardless of in vivo or in vitro development. Preimplantation cow embryos produced by in vitro procedures expressed mRNAs for catalase, CuZn-SOD and GPX, whereas transcripts for Mn-SOD were not detected at any stage. GCS transcripts, although present in stages up to the morula, were not detected in cow blastocysts. Analysis of antioxidant gene expression in both bovine primary oviductal cell monolayer cultures and nonattached, ciliated oviductal cell vesicle cultures revealed a constitutive pattern of expression of all five enzymes for the 8-day culture interval. These experiments suggest that differences in gene expression may contribute to the variation in the ability of embryos to develop in vitro with respect to levels of oxygen and dependence on coculture.

G12 requirement for thrombin-stimulated gene expression and DNA synthesis in 1321N1 astrocytoma cells

Thrombin stimulation of 1321N1 astrocytoma cells leads to Ras-dependent AP-1-mediated transcriptional activation and to DNA replication. In contrast to what has been observed in most cell systems, in 1321N1 cells these responses are pertussis toxin-insensitive. The pertussis toxin-insensitive G-protein G12 has been implicated in cell growth and transformation in different cell systems. We have examined the potential role of this protein in AP-1-mediated transcriptional activation and DNA synthesis in 1321N1 cells. Transient expression of an activated (GTPase-deficient) mutant of G alpha 12 increased AP-1-dependent gene expression. This response was inhibited by co-expression of a dominant negative Ala-15 Ras protein. To determine whether the pertussis toxin-insensitive G12 protein is involved in the thrombin-stimulated DNA synthesis, an inhibitory antibody against the C-terminal sequence of G alpha 12 subunit was microinjected into 1321N1 cells. Microinjection of the anti-G alpha 12 resulted in a concentration-dependent inhibition of thrombin-stimulated DNA synthesis. In contrast, microinjection of nonimmune IgG or an antibody directed against the C terminus of G alpha o did not reduce the mitogenic response to thrombin. Furthermore, microinjection of the anti-G alpha 12 antibody had no effect on fibroblast growth factor-stimulated DNA synthesis. These results demonstrate a specific role for G alpha 12 in the mitogenic response to thrombin in human astroglial cells.

Cross-resistance studies on two K562 sublines resistant to diaziridinylbenzoquinones

Two resistant K562 sublines have been developed by treatment with AZQ (2,5-bis(carboethoxyamino)-3,6-diaziridinyl-1,4-benzoquinone) and BZQ (2,5-bis(2-hydroxyethylamino)-3,6-diaziridinyl-1,4-benzoquinone). The ID50 values of for AZQ on K562, the AZQ-resistant sublines (AZQR) and the BZQ-resistant sublines (BZQR) were 0.063, 1.47 and 0.244 microM, respectively. The relative ID50 values for BZQ on the same cell lines were 0.2, 0.67 and 0.83 microM, respectively. Although it is generally believed that these two quinones function by different mechanisms, the two sublines have similar decreased levels of cytochrome P-450 reductase and DT-diaphorase and increased levels of glutathione and superoxide dismutase, compared to the parent cell line. The sublines are also cross-resistant to adriamycin, mitozolamide, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and mitomycin C. This work indicates the potential multifactorial mechanisms by which drug resistance can be induced in cell lines in the absence of conventional 'P'-glycoprotein multidrug resistance.

Poly(adenosine diphosphate ribose) polymerase inhibition prevents necrosis induced by H2O2 but not apoptosis

BACKGROUND & AIMS

H2O2 causes DNA damage, which activates poly(adenosine diphosphate ribose) polymerase (PARP), a nuclear enzyme that uses nicotinamide adenine dinucleotide (NAD) as a substrate. When DNA strand breaks are extensive, consumption of NAD by PARP can cause adenosine triphosphate depletion. The aim was to study the effect of PARP inhibition on H2O2-induced cell injury in the intestinal epithelial cell line HT-29-18-C1.

METHODS

Cell injury was assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide test and flow cytometric analysis.

RESULTS

The PARP inhibitors 3-aminobenzamide and nicotinamide both prevented cell death immediately after exposure to 1 mmol/L H2O2 and loss of cellular NAD and adenosine triphosphate. The inactive structural analogues 3-aminobenzoic acid and nicotinic acid had no such protective effect. H2O2 also caused HT-29 cells to detach from the monolayer up to 24 hours after exposure and die by apoptosis in the incubating medium. Flow cytometric analysis showed that 3-aminobenzamide had no effect on this delayed detachment process.

CONCLUSIONS

H2O2 induces two distinct death pathways in HT-29 cells: one that is immediate and may represent necrosis and another that is delayed, causing cell detachment leading to apoptosis. PARP inhibition prevents necrosis but has no effect on delayed cell detachment leading to apoptosis.

Review article: manipulation of cell death--the development of novel strategies for the treatment of gastrointestinal disease

The mechanisms underlying cell death are reviewed in order to propose new targets for the therapy of gastrointestinal disease. Necrosis is a set of precise biochemical and cellular lesions which culminate in cell destruction. A number of potential targets for drug therapy are discussed which will inhibit necrosis, including preservation of cellular ATP by inhibition of poly(ADP-ribose) polymerase. Such therapies may be useful either as adjuncts to other therapeutic modalities such as immunosuppressive agents for the treatment of inflammatory conditions or on their own for organ preservation prior to organ transplantation. Either excessive apoptosis or failure of apoptosis plays an important role in a variety of gastrointestinal diseases. Failure of apoptosis is of particular importance in the development of colorectal cancer. Mutations or deletions of p53, bcl-2 and myc prevents the appropriate deletion of malignant cells and causes resistance to anti-cancer drugs which act by the induction of apoptosis. Correction of these genetic defects or replacement of their function is a major strategy in cancer prevention and therapy. It is concluded that manipulation of cell death processes is an important new area for gastrointestinal research.

Differential expression of bcl-2 in intestinal epithelia. Correlation with attenuation of apoptosis in colonic crypts and the incidence of colonic neoplasia

The cell-positional incidence of both spontaneous and damage-induced apoptosis of epithelial cells was assessed in longitudinal sections of the crypts of small intestine and colon of BDF1 mice. This was compared, using immunohistochemistry, with the pattern of expression of bcl-2, a suppressor of apoptosis. In the small intestine, apoptosis was maximal around cell position 4 from the base of the crypt; this closely corresponds to the position considered to contain the stem cells. In the colon, however, apoptosis was not confined to the area considered to harbour the stem cells (position 1 and 2). Instead, apoptosis was attenuated and distributed along the length of the crypt. Some cells at the base of murine colonic crypts expressed bcl-2 protein, whereas bcl-2 was absent in the crypts of the small intestine. Most pertinently, bcl-2 was absent from small intestinal crypt cells at positions 4–5 (the stem cell region). The importance of the expression of bcl-2 to the attenuation of apoptosis in stem cells was confirmed by analysis of the levels of both spontaneous and induced apoptosis in homozygously bcl-2 null C57BL/6 mice: in colonic crypts the level of spontaneous apoptosis rose significantly, and selectively at the base of the crypt, in comparison with crypts from wild-type animals. In contrast, there was no rise in spontaneous apoptosis in the small intestinal crypts from the bcl-2 null animals. Analysis of sections of human colon and small intestine also showed that expression of bcl-2 was confined to the base of the colonic crypt. The attenuation of apoptosis by bcl-2 in the region of the stem cells of the colonic crypts may dispose these to neoplastic transformation. Indeed, analysis of human carcinomas revealed expression of bcl-2, which in some samples was reciprocal with the expression of p53.

O6-benzylguanine increases the sensitivity of human primary bone marrow cells to the cytotoxic effects of temozolomide

The sensitivity of human primary bone marrow granulocyte/macrophage precursor cells to the cytotoxic effects of the methylating antitumor agent temozolomide (8-carbamoyl-3- methylimidazo[5,1-d]-1,2,3,5-tetrazin-4-[3H]-1) was investigated using an in vitro colony-forming assay. In the eight samples examined, there was a range of sensitivities with D37 values from 18.2 to > 55 microM. When cells were simultaneously exposed to the O6-alkylguanine-DNA alkyltransferase (ATase) inactivating agent, O6-benzylguanine (O6BeG; 10 microM), the cytotoxicity of temozolomide was substantially increased with D37 values between 5 and 38.5 microM. O6BeG also increased temozolomide sensitivity in the human colon carcinoma cell line, WiDr, and this was shown to correlate with the O6BeG-mediated depletion of ATase activity. Where the extent of sensitization produced by O6BeG could be calculated, there was a correlation between this and the D37 value in the absence of O6BeG (R = 0.996); thus, sensitization was more extensive in the cells that were inherently more resistant to temozolomide. These data have implications for possible increased hematological toxicity in clinical protocols designed to exploit O6BeG or other agents to deplete ATase activity in tumors cells prior to treatment of patients with temozolomide or related agents.

Characterisation of oxidative injury to an intestinal cell line (HT-29) by hydrogen peroxide

Reactive oxygen metabolites have been implicated in causing epithelial cell injury in colonic inflammation. A model of oxidant injury in intestinal epithelial cells has been developed in which HT-29-18-C1 cells are injured with graded concentrations of hydrogen peroxide and characterised by the MTT test. The MTT test was validated as a cytotoxicity assay and has a similar sensitivity to hydrogen peroxide induced injury as the assay of intracellular adenosine triphosphate. Exposure to a range of hydrogen peroxide concentrations (0.05-20 mM) for varying duration (5-120 min) showed that injury was dependent on time and concentration. The median lethal dose (LD50) for one hour exposure to hydrogen peroxide was approximately 0.1 mM. Injury from hydrogen peroxide was only partially reversible as determined by the MTT test and assay of cellular proliferation by crystal violet staining. There was an exponential loss of hydrogen peroxide when incubated with HT-29-18-C1 cells (t1/2 35 min). Experiments with 0.5 mg/ml aminotriazole and 0.5-2 mM buthionine sulphoximine suggested hydrogen peroxide breakdown was predominantly caused by catalase rather than glutathione peroxidase. Injury resulting from 1 mM hydrogen peroxide could be reduced by either coincubation of cells with 1,10-phenanthroline, an Fe2+ chelator, or preincubation with deferoxamine, and Fe3+ chelator, suggesting the participation of Fe2+ and Fe3+ in hydrogen peroxide induced injury. In conclusion, hydrogen peroxide induces injury in HT-29-18-C1 cells both directly and by generation of the hydroxyl radical.

A fifth member of the mammalian G-protein beta-subunit family. Expression in brain and activation of the beta 2 isotype of phospholipase C

The beta-subunits of the heterotrimeric GTP-binding proteins (G-proteins) are important regulators of G-protein alpha-subunits as well as of certain signal transduction receptors and effectors. We have identified a fifth member of the G-protein beta-subunit family, G beta 5, by molecular cloning. Sequence analysis of recombinant clones revealed an open reading frame of 1,059 base pairs, potentially encoding a protein of 353 amino acids having 53% identity to previously identified G beta-subunit proteins. Northern blot analysis of poly(A)-selected mRNA prepared from different mouse tissues demonstrated that G beta 5 is predominantly expressed in adult brain as two transcripts of 2.3 and 1.75 kilobases. A G beta 5-specific antiserum detected a band of 39.3 kilodaltons on immunoblots of crude membrane proteins isolated from normal mouse brain but not from other tissues. Using a transient cotransfection assay, we showed that a plasmid construct expressing the G beta 5 open reading frame, when coexpressed with different G-protein gamma (G gamma)-subunits, can stimulate the activity of the beta 2 isoform of phosphoinositide-specific phospholipase C (PLC beta 2). The stimulation of PLC beta 2 was most pronounced when G beta 5 was co-expressed with G gamma 2, although activation was observed when G beta 5 was cotransfected with either G gamma 1, G gamma 3, G gamma 5, or G gamma cone. These results prove that G beta 5 can functionally associate with G gamma proteins and is therefore a bona fide member of the G beta protein family. The rather low level of identity between G beta 5 and the other mammalian G beta-subunits may shed light on structural/sequence elements necessary for G beta protein function.

Rapid computerized analysis of Na+/H+ exchange flux

The regulation of intracellular pH (pHi) is mediated by membrane transporters whose activity is directly controlled by pHi. Therefore, transport rates must be compared at identical pHi values in functional studies of these transporters. This is conventionally performed using scatter plots showing initial rates of proton flux versus intracellular pH. We present justification for determining proton flux over a wide range of pHi, by digitally smoothing a pHi trace and then directly taking the first derivative versus time of smoothed data. Compared to conventional least-squares analysis of initial rates, the derivative method generates much more information per experiment. Compared to other methods which fit pHi traces to a defined equation prior to rate calculation, the new method does not require that the pHi trace be well fit by any given mathematical function. The derivative technique is illustrated in an analysis of Na+/H+ exchange in Caco-2 cells. Intracellular pH is measured fluorometrically in cells loaded with BCECF (2',7'-bis[2-carboxyethyl]-5-(and-6)carboxyfluorescein). To validate the analysis of Na+/H+ exchange over an extended time range, we demonstrate that cellular acidification with NH4Cl does not change steady state Na+ content. We find that proton flux rates analyzed by the derivative method are equivalent to initial rates measured by least-squares analysis.

Preimplantation development of in vitro-matured and in vitro-fertilized ovine zygotes: comparison between coculture on oviduct epithelial cell monolayers and culture under low oxygen atmosphere

The roles of medium composition, serum source, embryo coculture, and culture under low O2 conditions on the development of in vitro-matured and in vitro-fertilized (IVMF) ovine zygotes were investigated in three separate experiments. In the first experiment, the proportion of cocultured IVMF zygotes developing to the blastocyst stage was significantly higher (38.0% vs. 3.5%; p < 0.05) than that of non-cocultured zygotes treated within three embryo culture media (TCM-199 + 10% fetal bovine serum [FBS]; bicarbonate-buffered, glucose-free synthetic oviduct fluid medium [mod-SOFM] + 10% FBS; and bicarbonate-buffered BSA-free Tyrode's salt solution [mod-TALP] + 10% FBS) under a 5% CO2 atmosphere in air. In a second experiment, a significantly higher (p < 0.05) proportion of cocultured zygotes placed in TCM-199 medium survived to the blastocyst stage (37.4% blastocysts vs. 23.4% in mod-SOFM). No significant effect of serum (FBS vs. human serum [HS]) was observed on embryonic development, but coculture was confirmed to exert a significant influence on development to the blastocyst stage. In the final experiment, survival of the embryo under a reduced oxygen (5% CO2:5% O2:90% N2) atmosphere was investigated. In contrast to results in the initial experiments, embryonic survival was significantly higher (p < 0.05) in the non-cocultured treatment groups (21.9% blastocysts vs. 0.4% for cocultured zygotes). Serum source also had a significant (p < 0.05) influence upon the development of non-cocultured zygotes: 32.3% of zygotes cultured with HS progressed to the blastocyst stage vs. 11.5% of zygotes cultured in FBS-supplemented medium. These results have characterized two distinct culture environments, each capable of supporting the development of high frequencies of unselected IVMF zygotes to the blastocyst stage in vitro.

A growth factor phenotype map for ovine preimplantation development

The reverse transcription-polymerase chain reaction (RT-PCR) was used to determine the patterns of expression for several growth factor ligand and receptor genes during ovine preimplantation development. Transcripts for insulin-like growth factor (IGF)-I, IGF-II, and the receptors for insulin and IGF-I were detected throughout ovine preimplantation development from the 1-cell to the blastocyst stage. Transforming growth factor alpha (TGF alpha) transcripts were also detected throughout ovine preimplantation development. The mRNAs encoding basic fibroblast growth factor (bFGF) were detected in all stages of the ovine preimplantation embryo, although the relative abundance of this transcript consistently decreased from the 1-cell to the blastocyst stage, suggesting that it may represent a maternal transcript in early sheep embryos. Transcripts encoding ovine trophoblast protein (oTP) were detected only within blastocyst-stage embryos. Primary ovine oviduct cell cultures express the transcripts for IGF-II, IGF-I, TGF alpha, bFGF, TGF beta 1, and the receptors for insulin and IGF-I, suggesting that paracrine growth factor circuits may exist between the oviduct epithelium and the early ovine embryo. Transcripts for insulin, epidermal growth factor (EGF), and nerve growth factor (NGF) were not detected in any stage of the ovine preimplantation embryo or within the oviduct cell preparations. The expression of growth factor transcripts very early in mammalian development would predict that these molecules fulfil a necessary role(s) in supporting the progression of early embryos through the preimplantation interval. Our future efforts will be directed to understanding the nature of these putative regulatory pathways.

A pyruvate decarboxylase gene from Aspergillus parasiticus

A gene encoding a putative pyruvate decarboxylase (EC 4.1.1.1) was isolated from a genomic library of the filamentous fungus Aspergillus parasiticus strain SU-1. The deduced amino acid sequence showed 37% homology to PDC1 from Saccharomyces cerevisiae. Although A. parasiticus has an obligate growth requirement for oxygen, it produced ethanol in shake flask cultures indicating a response to anoxic conditions mediated by pyruvate decarboxylase.

Possible roles of insulin and insulin-like growth factors in rat preimplantation development: investigation of gene expression by reverse transcription-polymerase chain reaction

The sensitive mRNA phenotyping technique of reverse transcription-polymerase chain reaction was used to demonstrate that insulin receptor mRNA is present in rat embryos during the preimplantation period. In addition, mRNA encoding insulin-like growth factor (IGF) type I and type II receptors have also been detected in rat preimplantation embryos. IGF-I mRNA was not detected in preimplantation embryos but was found in oviducts and uteri of prepubertal and early pregnant rats. IGF-II mRNA was present in both embryos and in oviducts and uteri during the preimplantation period. These findings suggest that insulin and IGF-I could influence early embryo development in endocrine or in paracrine fashions, whereas IGF-II may have an additional autocrine mode of action in affecting preimplantation embryos in rats.

The relationship of provider organizational status and erythropoietin dosing in end stage renal disease patients

Controversy exists as to whether provider organizational characteristics such as profit status and setting are associated with the content of medical care or efficiency with which care is rendered. Following FDA approval of human recombinant erythropoietin (EPO) for use in clinical practice, Medicare approved coverage for beneficiaries in its end stage renal disease program and established a fixed payment per dose. Because cost of EPO administration varied positively with dose, providers could realize larger profit with prescription of smaller doses. We used Medicare claims data to assess EPO use by renal dialysis providers one year after FDA approval (June 1990) as a function of provider ownership (for-profit, not-for-profit, government agency) and setting (hospital-based, free-standing). Mean dose of EPO was 236 units greater (P = 0.0001) for not-for-profit freestanding facilities, 593 units greater (P = 0.0001) for government facilities, and 555 units greater for not-for-profit hospitals (P = 0.0001) than among for-profit freestanding providers. With fixed payment per dose of EPO, for-profit, freestanding providers prescribed EPO more often and administered smaller doses than not-for-profit or government providers, behavior that is consistent with profit maximization.

Domestic cases of hemorrhagic fever with renal syndrome in the United States

Although serologic studies have identified hantaviral infection in the United States, acute disease has not been recognized. This study describes 3 cases of domestically acquired hemorrhagic fever with renal syndrome (HFRS) in the United States. Infection was due to a local strain of Seoul virus (Baltimore rat virus). A review of the clinical features indicated a mild illness characterized by nausea, vomiting, renal and liver failure similar to HFRS described elsewhere for rat-borne viruses. Follow-up of 2 patients identified persistent hypertension and renal disease providing further evidence of an association between past hantaviral infection and hypertensive renal disease.

Effect of recombinant erythropoietin on hospital admissions, readmissions, length of stay, and costs of dialysis patients

To examine the effects of recombinant human erythropoietin (rHuEPO) on hospital utilization, hospital costs, and Medicare reimbursements for hospital care, a longitudinal, matched cohort study was conducted using Medicare claims data of 23,806 Medicare-eligible, dialysis patients who received rHuEPO, did not have a transplant, and were alive for 18 mo or longer and 22,720 controls matched on age, sex, race, cause of ESRD, and dialysis modality. The relative odds (rHuEPO versus control) of admission for all causes and for specific causes over 9 mo, adjusted for admission in the prior 9 mo and the per patient change in total admissions, inpatient days, hospital costs, and Medicare hospital payments between the prior 9-mo period and the subsequent 9-mo period was examined. The adjusted relative odds (95% confidence interval) of admission (rHuEPO versus control) was: higher and statistically significant for all causes, 1.08 (1.03 to 1.14); seizure, 1.52 (1.28 to 1.75); vascular access revision, 1.11 (1.06 to 1.17), and heart failure, 1.17 (1.09 to 1.26); higher but not statistically significant for angina, 1.09 (0.99 to 1.20) and stroke, 1.08 (0.86 to 1.31); and lower but not statistically significant for myocardial infarction, 0.91 (0.72 to 1.10); peripheral vascular disease, 0.81 (0.60 to 1.02); anemia, 0.86 (0.56 to 1.17); and depression, 0.89 (0.37 to 1.40). The mean change per 1,000 patients in admissions was less by 38 (P = 0.03) because of fewer readmissions, and in days was 1,309 less (P < 0.001), for patients treated with rHuEPO versus controls. The mean change per patient in hospital costs was $371 less and was statistically significant (P = 0.03) and in Medicare hospital payments was $132 less but was not statistically significant (P = 0.43) for patients treated with rHuEPO versus controls. rHuEPO was associated with an increase in the probability of hospital admission (particularly admissions potentially related to adverse effects) but a decrease in readmissions, overall admissions, hospital days, and cost to hospitals in this cohort of patients surviving for 18 mo. Although not realized short term, Medicare savings from potential rHuEPO-related reductions in hospital care may be long term through future adjustments in diagnosis-related group-based hospital payment.

A review of the first year of Medicare coverage of erythropoietin

Recombinant human erythropoietin (rHuEPO) is a new drug for treating anemia associated with end stage renal disease (ESRD). In a study of rHuEPO diffusion, costs, and effectiveness, we analyze ESRD program data and all claims submitted to Medicare for reimbursement of rHuEPO administered to ESRD dialysis patients. Access to rHuEPO was rapid and extensive during the first year of Medicare coverage. Dosing of rHuEPO and achieved hematocrit were lower than expected based on the results of clinical trials. rHuEPO cost Medicare $144 million in its first year. The analysis of insurance claims data allowed effective monitoring of access, costs, and effectiveness of this new biotechnology.