Hypoxaemia and release of endothelin-1

BACKGROUND: Secretion of the vasoconstrictor peptide endothelin-1 from vascular endothelium is increased by various stimuli. Whether hypoxaemia affects plasma levels of endothelin-1 in humans is unknown, but this may be important in the haemodynamic response to hypoxaemia. The plasma endothelin-1 concentrations in hypoxaemic humans has therefore been measured. METHODS: Plasma levels of endothelin-1 were measured by specific radioimmunoassay in 10 control subjects at rest and following 30 minutes of acute hypoxaemia (SaO2 75-80%) induced by breathing a nitrogen/oxygen mixture, and in 10 patients with hypoxaemic cor pulmonale. RESULTS: The plasma endothelin-1 concentration in control subjects was increased from a mean (SE) of 0.90 (0.11) pmol/l at baseline to 2.34 (0.34) pmol/l during hypoxaemia. In patients with cor pulmonale the plasma endothelin-1 concentration was 2.96 (0.34) pmol/l, raised in comparison with control subjects at rest but similar to levels in controls during hypoxaemia. CONCLUSIONS: Plasma levels of endothelin-1 were increased by hypoxaemia in humans. The raised levels observed in patients with cor pulmonale may largely be attributable to the effects of hypoxaemia, although the pathophysiological significance of these observations remains to be established.     

Immunological and virological analyses of persons infected by human immunodeficiency virus type 1 while participating in trials of recombinant gp120 subunit vaccines

We have studied 18 participants in phase I/II clinical trials of recombinant gp120 (rgp120) subunit vaccines (MN and SF-2) who became infected with human immunodeficiency virus type 1 (HIV-1) during the course of the trials. Of the 18 individuals, 2 had received a placebo vaccine, 9 had been immunized with MN rgp120, and seven had been immunized with SF-2 rgp120. Thirteen of the 18 infected vaccinees had received three or four immunizations prior to becoming infected. Of these, two were placebo recipients, six had received MN rgp120, and five had received SF-2 rgp120. Only 1 of the 11 rgp120 recipients who had multiple immunizations failed to develop a strong immunoglobulin G antibody response to the immunogen. However, the antibody response to rgp120 was transient, typically having a half-life of 40 to 60 days. No significant neutralizing activity against the infecting strain was detected in any of the infected individuals at any time prior to infection. Antibody titers in subjects infected despite vaccination and in noninfected subjects were not significantly different. Envelope-specific cytotoxic T-lymphocyte responses measured after infection were infrequent and weak in the nine vaccinees who were tested. HIV-1 was isolated successfully from all 18 individuals. Sixteen of these strains had a non-syncytium-inducing (NSI) phenotype, while two had a syncytium-inducing (SI) phenotype. NSI strains used the CCR5 coreceptor to enter CD4+ cells, while an SI strain from one of the vaccinees also used CXCR4. Viruses isolated from the blood of rgp120 vaccinees were indistinguishable from viruses isolated from control individuals in terms of their inherent sensitivity to neutralization by specific monoclonal antibodies and their replication rates in vitro. Furthermore, genetic sequencing of the env genes of strains infecting the vaccinees did not reveal any features that clearly distinguished these viruses from contemporary clade B viruses circulating in the United States. Thus, despite rigorous genetic analyses, using various breakdowns of the data sets, we could find no evidence that rgp120 vaccination exerted selection pressure on the infecting HIV-1 strains. The viral burdens in the infected rgp120 vaccine recipients were also determined, and they were found to be not significantly different from those in cohorts of placebo-vaccinated and nonvaccinated individuals. In summary, we conclude that vaccination with rgp120 has had,to date, no obvious beneficial or adverse effects on the individuals we have studied.     

Oestrogen-regulated genes in breast cancer: association of pLIV1 with response to endocrine therapy

Northern hybridization analyses of the oestrogen-inducible mRNAs pLIV1 and pS2 were compared with oestrogen receptor (ER) immunocytochemistry assessments in 40 untreated primary or early recurrent breast tumours. Significant associations were observed between pLIV1/ER (P < 0.03), pS2/ER (P < 0.001) and pLIV1/pS2 (P < 0.04) status. After disease recurrence, patients were treated with assessable courses of endocrine therapies. Positive pLIV1, pS2 and ER statuses in primary disease were consequently found to be predictive of endocrine responsiveness in the secondary lesions (P < 0.03, P < 0.02, P < 0.005 respectively). However, despite these associations, a number of pLIV1- and/or pS2-positive tumours failed to respond to therapy.     

Application of high field spectroscopic imaging in the evaluation of temporal lobe epilepsy

Previous spectroscopic imaging studies of temporal lobe epilepsy have used comparisons of metabolite content or ratios to lateralize the seizure focus. Although highly successful, these studies have shown significant variations within each of the groups of healthy subjects and patients. This variation may arise from the natural differences seen in metabolite concentration in gray and white matter, the complex anatomy seen about the hippocampus, and the large voxels typically employed at 1.5 T. Using a 4.1 T whole body system, we have acquired spectroscopic images with 0.5 cc nominal voxels (1 cc after filtering) to evaluate the regional variation in metabolite content of the hippocampus, temporal gray and white matter, midbrain, and cerebellar vermis. Using a threshold value of 0.90 for CR/NAA, a value 90% of all normal hippocampal voxels lay below, we have correctly identified the presence of epileptogenic tissue in patients with unilateral as well as bilateral seizures. By using comparisons to healthy values of the CR/NAA ratio, this method enables the visualization of bilateral disease and provides information on the extent of gray matter involvement.     

Multiwavelength spectrophotometric determination of acid dissociation constants of ionizable drugs

A multiwavelength spectrophotometric approach has been developed to determine acid dissociation constants (pKa values) of sparingly soluble drug compounds. UV absorption spectra of the drug solution are acquired using a versatile device based on a fiber optics dip probe, a light source and a photodiode array (PDA) detector while the PH and the ionic strength of the chemical system is manipulated precisely by means of a commercially available titrator. Target factor analysis (TFA) has been applied to deduce the pKa values from the multiwavelength UV absorption data recorded at different pH values. We have called this multiwavelength approach the WApH technique because the pKa results are determined from changes in Wavelength and Absorbance as a function of pH (WApH). The WApH technique is exemplified by using several pure drugs, namely, niflumic acid, nitrazepam, pyridoxine, quinine and terbutaline. The pKa values obtained agree well with those derived from pH-metric titrations. It has been demonstrated that the WApH technique is able to deduce pKa values with high accuracy even if the absorption spectra of the reacting species are very similar.     

Estradiol induction of retinoic acid receptors in human breast cancer cells

Retinoic acid inhibits proliferation and steroid receptor gene expression in human breast cancer cell lines. Retinoic acid receptors (RAR)alpha, -beta, and -gamma are expressed in these cells and the expression of RAR alpha is significantly greater in estrogen receptor (ER)-positive cells. This study was undertaken to determine whether the same relationship between RAR alpha and ER gene expression was present in human breast cancers and to explore the possibility that the higher level of RAR alpha in ER-positive cells was due to estrogen regulation of RAR alpha gene expression. RAR alpha and ER mRNA expression were determined by Northern blot analysis in 116 primary breast tumors; 94 (81%) tumors were ER-positive and of these 87 (93%) were also RAR alpha-positive. The coexpression of ER and RAR alpha was statistically significant (P = 0.0052 by chi 2 contingency analysis). There was also a positive correlation (by linear regression analysis) between the levels of expression of ER and RAR alpha mRNA (r2 = 0.251, P = 0.0001), which confirmed the relationship previously documented in breast cancer cell lines and suggested that RAR alpha expression may be modulated in breast cancer in vivo by estrogens acting via the ER. The ability of estradiol to regulate RAR alpha gene expression was examined in vitro using T-47D cells which had been rendered sensitive to estrogen by repeated passage in steroid-depleted medium. Estradiol increased RAR alpha gene expression, but not that of RAR beta or RAR gamma, in a concentration-dependent manner, with the effect being maximal at 10(-10) M and less marked at higher concentrations. The effect was rapid, being detectable 1 h after and maximal 6 h after treatment with 10(-10) M estradiol. Co-treatment of cells with estradiol and antiestrogens (tamoxifen or ICI 164384, 4 x 10(-7) M for 6 h) inhibited the estradiol induction of RAR alpha gene expression, demonstrating that the effect was ER mediated. The estradiol sensitivity of the effect was underscored by the demonstration that addition of untreated serum to cells growing under steroid-depleted conditions was sufficient to induce maximal RAR alpha gene expression. This effect was totally abolished by addition of ICI 164384. In summary, the demonstration that estradiol increased RAR alpha mRNA levels in breast cancer cells supports the hypothesis that the correlation between RAR alpha and ER gene expression in breast tumors and breast cancer cell lines is due to estradiol augmentation of RAR alpha gene expression.     

Effects of cytosine arabinoside on human leukemia cells

Cytosine arabinoside (Ara-C) is used to treat leukemias, with complete remission induced by combination chemotherapy in approximately 70% of cases of acute myelogenous leukemia (AML). Ara-CTP acts as a competitive inhibitor of DNA polymerase and may also be incorporated into DNA. Accumulation of deoxyribonucleoside triphosphates (dNTPs) induced by Ara-C may indicate disruption of DNA synthesis in susceptible leukemia cells. A procedure has been developed for the quantification of Ara-CTP and dNTPs from small samples of leukaemia cells from patients (4 x 10(7) cells) activated with concanavalin A (10 micrograms/ml, 48 hr) and grown in the presence of [32P]orthophosphate (1.1 microM, 9 x 10(6) Ci/mol, 16 hr). The susceptibilities to Ara-C of the human leukemia cell lines CCRF-CEM (IC50 = 6.30 nM), CCRF-HSB-2 (IC50 = 10.4 nM) and MOLT-4 (IC50 = 10.0 nM) may be correlated with their abilities to accumulate high concentrations of Ara-CTP (> 1000 amol/cell) with increases of between 1.3- and 3.4-fold in dATP, dGTP and dTTP for the four cell lines, while dCTP decreased between 0.23- and 0.78-fold. By contrast, an Ara-C-resistant derivative of HL-60 cells (IC50 = 400 nM) accumulated only low concentrations of Ara-CTP (71 amol/cell) without significant changes in dNTPs. High concentrations of Ara-CTP in leukemia cells induce accumulations of dATP, dGTP and dTTP due to inhibition of DNA synthesis, and depletion of dCTP. This imbalance in the pools of the four dNTPs could lead to genetic miscoding and cell death.     

Induction chemotherapy followed by breast conservation for locally advanced carcinoma of the breast

BACKGROUND: Few women with locally advanced breast cancer remain disease-free, even for 2 years. Response to induction chemotherapy may be associated with longer disease-free and overall survival rates. The role of breast conservation in selected patients with response to induction chemotherapy was evaluated. METHODS: Since 1979, patients with Stages IIB and III breast cancer have undergone induction chemotherapy; patients with response continued chemotherapy until a plateau of regression was achieved. Before 1983, all patients having a response to chemotherapy underwent mastectomy; since 1983, selected patients have undergone breast conservation. Outcomes were tallied comparing these two groups of patients. RESULTS: The study group included 189 women, who were followed up for 12-159 months (median, 46 months) after diagnosis. Of the patients, 85% had a response to induction chemotherapy. Patients with no response were excluded from additional consideration in this study. One hundred three (64%) women underwent mastectomy; 55 (36%) were treated with breast conservation. The disease-free 5-year survival rate was 61% for all patients with a response to chemotherapy; 56% for those having mastectomy and 77% for those having breast conservation. The overall 5-year survival rate was 69% for all patients with a response to chemotherapy, 67% for those undergoing mastectomy and 80% for those having breast conservation. CONCLUSIONS: Induction chemotherapy achieves significant tumor regression in most women with locally advanced breast cancer, permitting subsequent breast conservation or mastectomy with a greater expectation of long-term success. Breast conservation is used more frequently with the same expectation of success as mastectomy, presuming careful selection based on response to chemotherapy.