Validation of a shortened MR imaging protocol for pediatric spinal pathology.

OBJECTIVE: Conventional pediatric spine MRI protocols have multiple sequences resulting in long acquisition times. Sedation is consequently required. This study evaluates the diagnostic capability of a limited MRI spine protocol for selected common pediatric indications. METHODS: Spine MRIs at CHEO between 2017 and 2020 were reviewed across pediatric patients younger than four years old. Two blinded neuroradiologists reviewed limited scan sequences, and results were independently compared to previously reported findings from the complete imaging series. T2 sagittal sequences from the craniocervical junction to sacrum and T1 axial sequence of the lumbar spine constitute the short protocol, with the outcomes of interest being cerebellar ectopia, syrinx, level of conus, filum < 2 mm, fatty filum, and spinal dysraphism. RESULTS: A total of 105 studies were evaluated in 54 male and 51 female patients (mean age 19.2 months). The average combined scan time of the limited sequences was 15 min compared to 35 min for conventional protocols (delta = 20 min). The average percent agreement between full and limited sequences was > 95% in all but identifying a filum < 2 mm, where the percent agreement was 87%. Using limited MR sequences had high sensitivity (> 0.91) and specificity (> 0.99) for the detection of cerebellar ectopia, syrinx, fatty filum, and spinal dysraphism. CONCLUSION: This study demonstrates that selected spinal imaging sequences allow for consistent and accurate diagnosis of specific clinical conditions. A limited spine imaging protocol has potential as a screening test to reduce the need for full-sequence MRI scans. Further work is needed to determine utility of selected imaging for other clinical indications.

Prognostic Accuracy of Fetal MRI in Predicting Postnatal Neurodevelopmental Outcome.

BACKGROUND AND PURPOSE: The superior diagnostic accuracy of fetal MR imaging in detecting fetal brain abnormalities has been previously demonstrated; however, the ability of fetal MR imaging to prognosticate postnatal outcome is not well-studied. We performed a retrospective analysis to determine the prognostic accuracy of fetal MR imaging in predicting postnatal neurodevelopmental outcome. MATERIALS AND METHODS: We identified all fetal MR imaging performed at the Children's Hospital of Eastern Ontario during a 10-year period and assessed agreement between prenatal prognosis and postnatal outcome. Prenatal prognosis was determined by a pediatric neurologist who reviewed the fetal MR imaging report and categorized each pregnancy as having a favorable, indeterminate, or poor prognosis. Assessment of postnatal neurodevelopmental outcome was made solely on the basis of the child's Gross Motor Function Classification System score and whether the child developed epilepsy. Postnatal outcome was categorized as favorable, intermediate, or poor. We also assessed the diagnostic accuracy of fetal MR imaging by comparing prenatal and postnatal imaging diagnoses. RESULTS: We reviewed 145 fetal MR images: 114 were included in the assessment of diagnostic accuracy, and 104 were included in the assessment of prognostic accuracy. There was 93.0% agreement between prenatal and postnatal imaging diagnoses. Prognosis was favorable in 44.2%, indeterminate in 50.0%, and poor in 5.8% of pregnancies. There was 93.5% agreement between a favorable prenatal prognosis and a favorable postnatal outcome. CONCLUSIONS: A favorable prenatal prognosis is highly predictive of a favorable postnatal outcome. Further studies are required to better understand the role of fetal MR imaging in prognosticating postnatal development, particularly in pregnancies with indeterminate and poor prognoses.

Can digital breast tomosynthesis perform better than standard digital mammography work-up in breast cancer assessment clinic?

PURPOSE: To compare the efficacy of use of digital breast tomosynthesis (DBT) with standard digital mammography (DM) workup views in the breast cancer assessment clinic. MATERIALS AND METHODS: The Tomosynthesis Assessment Clinic trial (TACT), conducted between 16 October 2014 and 19 April 2016, is an ethics-approved, monocenter, multireader, multicase split-plot reading study. After written informed consent was obtained, 144 females (age > 40 years) who were recalled to the assessment clinic were recruited into TACT. These cases (48 cancers) were randomly allocated for blinded review of (1) DM workup and (2) DBT, both in conjunction with previous DM from the screening examination. Fifteen radiologists of varying experience levels in the Australia BreastScreen Program were included in this study, wherein each radiologist read 48 cases (16 cancers) in 3 non-overlapping blocks. Diagnostic accuracy was measured by means of sensitivity, specificity, and positive (PPV) and negative predictive values (NPV). The receiver-operating characteristic area under the curve (AUC) was calculated to determine radiologists' performances. RESULTS: Use of DBT (AUC = 0.927) led to improved performance of the radiologists (z = 2.62, p = 0.008) compared with mammography workup (AUC = 0.872). Similarly, the sensitivity, specificity, PPV, and NPV of DBT (0.93, 0.75, 0.64, 0.96) were higher than those of the workup (0.90, 0.56, 0.49, 0.92). Most radiologists (80%) performed better with DBT than standard workup. Cancerous lesions on DBT appeared more severe (U = 33,172, p = 0.02) and conspicuous (U = 24,207, p = 0.02). There was a significant reduction in the need for additional views (χ2 = 17.63, p < 0.001) and recommendations for ultrasound (χ2 = 8.56, p = 0.003) with DBT. CONCLUSIONS: DBT has the potential to increase diagnostic accuracy and simplify the assessment process in the breast cancer assessment clinic. KEY POINTS: • Use of DBT in the assessment clinic results in increased diagnostic accuracy. • Use of DBT in the assessment clinic improves performance of radiologists and also increases the confidence in their decisions. • DBT may reduce the need for additional views, ultrasound imaging, and biopsy.

Lymph node metastasis: A bearing on prognosis in squamous cell carcinoma.

Nodal status is a significant predictor for survival of patients with oral squamous cell carcinoma (SCC), sentinel lymph node (SLN) biopsy, step sectioning of SLNs, and immunohistochemistry have changed the detection of tumor deposits in lymph nodes (LNs). The extent of LN metastasis is a major determinant for the staging and the prognosis of most human malignancies and often guides therapeutic decisions. Metastasis to regional lymph node (RLN) is a complex process. It is often associated with several clinical and pathological characteristics. The involvement of RLN is often, a harbinger for increased risk of metastasis. New knowledge in this area can enable the clinicians and pathologists to study and treat tumors in a more directed fashion. A molecular approach to factors that predicts the likelihood of RLN metastasis could eliminate the reoccurrence of the tumor in the form of "micrometastasis" and "skip" metastasis. The aim of this review is to discuss different modes of spread of metastasis in SCC.

Efficient control of air pollution through plants, a cost-effective alternative: studies on Dalbergia sissoo Roxb.

Plants can be used as both passive biomonitors and biomitigators in urban and industrial environments to indicate the environmental quality and to ameliorate pollution level in a locality. Many studies reveal that plants are negatively affected by the ambient levels of air pollutants. The present study was conducted to evaluate the impact of air pollution on comparative basis with reference to changes in photosynthetic pigments, plant height, leaves, as well as, biochemical parameters of plants of different sites around Udaipur city receiving varying levels of pollution load. The investigated tree species Dalbergia sissoo Roxb. (Family: Fabaceae) exhibited a reduction in various physiological and biochemical growth parameters that correspond with air pollution levels at different sites. The tree species growing in polluted and control areas were compared with respect to foliar dust load, leaf area, and chlorophyll and total carbohydrate and total protein concentration in the leaves. Our studies suggest that D. sissoo Roxb. can successfully be grown in an area for monitoring air pollution, where it is mild and droughts are common. It will prove as an ideal tree species to control pollution effectively beside acting as a shade tree and being a source of food for birds and animals. By plantation of D. sissoo Roxb., mitigative measure at the polluted sites to control generation of particulate matter and the air quality required can be ensured. Our results also confirm that industrial and vehicular air pollution level in Udaipur city is shifting beyond limits.

High-resolution computed tomography of 'hot tub' pneumonitis.

A case of pneumonitis following exposure to Mycobacterium avium intracellulare in an indoor home spa (hot tub) is presented. The patient complained of recurrent dyspnoea and wheezing. High-resolution CT showed centrilobular ground-glass nodules. Pathological correlation showed interstitial and bronchiolocentric granulomata. Biopsy cultures grew M. avium intracellulare. The patient condition improved following cessation of hot tub use.

Variability in vascular responsiveness between Mexican-Americans and White Americans.

Ethnic differences in vascular adrenergic responsiveness have been implicated to be a potentially important mechanism which may be responsible for some of the variations in haemodynamic patterns between races. These differences may account for the variability in the prevalence of hypertension in different groups. The main aim of this study was to determine whether there was a difference in venous responsiveness to the vasoactive agents, phenylephrine and isoproterenol, between Mexican-Americans and White Americans. Isoproterenol is a potent non-selective beta-adrenergic agonist, phenylephrine is an alpha1-selective adrenergic agonist. Using the dorsal hand vein compliance technique, dose-response curves were constructed for the two vasoactive agents in 10 Mexican-American and 10 White American volunteers. The maximal venoconstriction for phenylephrine in the Mexican-American group was significantly less than that of the Whites in the study (71.2 +/- 20.1% vs 89.4 +/- 10.9%, P < 0.05). The log ED50 for isoproterenol in the Mexican-American group was also significantly greater than that for Whites (1.68 +/- 0.35[47.6 ng/min] vs 1.19 +/- 0.55[15.5 ng/min], P < 0.05). These results suggest that Mexican-Americans have a differential responsiveness to adrenergic vasoactive agents compared to White Americans and may be protected from the development of hypertension.

CSF, plasma viral load and HIV associated dementia.

Plasma viral burden has proven valuable in predicting the future course of systemic HIV related disease and the response to treatment. It is not known whether plasma or cerebrospinal fluid (CSF) viral burden can be used to predict onset of or response to treatment of nervous system disease. We propose a model of viral load mediated neurotoxicity underlying peripheral and central HIV associated neurological disease. The objective of this preliminary study was to assess the relationship of HIV associated neurological disease to quantitative viral load in plasma and CSF. 47 subjects (HIV- = 10, HIV+ = 37) participated in the study. Plasma and CSF samples were collected within a 3 h window. RT-PCR (Roche Amplicor Monitor) was utilized to assess HIV-1 RNA viral load in both plasma and cell free (centrifuged) CSF. Subjects underwent concurrent comprehensive neurological and neuropsychological evaluations. In general, systemic viral load, as measured in plasma, was greater than that found in cell free CSF. Cell free CSF HIV RNA viral load was significantly correlated with neurological dysfunction, whereas plasma viral load was not. The sole subject with an elevated CSF viral load (> 5 Log 10), had HIV associated dementia (HAD) on clinical examination.

Safety and clinical utility of long-term intravenous milrinone in advanced heart failure.

Few data are available on the long-term safety or clinical utility of the inodilator agent milrinone. We designed a prospective, nonrandomized, observational trial in a cohort of 71 patients who had demonstrated dependence on inotropic therapy, had been clinically stable on an inotropic regimen (milrinone, dobutamine, or both) for > or = 72 hours, and had been given intravenous milrinone for > 72 hours. Group I (n = 22) patients required treatment with both milrinone and dobutamine to achieve stability; group II (n = 49) patients attained stability initially with either milrinone (subgroup IIA) or dobutamine (subgroup IIB), but later required adjunctive therapy with the other inotropic agent for continued hemodynamic support. Of the 71 patients, 38% required mechanical intervention to achieve hemodynamic stability, and 68% were successfully bridged to heart transplantation. Patients were maintained on milrinone therapy for as long as 8 weeks and demonstrated a low incidence of adverse cardiac (7%) or noncardiac (4%) events. Subgroup IIA (28%) had significantly less need than subgroup IIB (52%) for mechanical intervention using an intraaortic balloon pump (p = 0.05), although mortality rates while awaiting transplantation were statistically similar in subgroups IIA (28%) and IIB (35%). Significant improvements from baseline values were noted at the time of transplantation for all aspects of systemic hemodynamics, indicating sustained long-term hemodynamic effects. Long-term intravenous milrinone therapy is safe and well tolerated, and it provides hemodynamic and metabolic support as a pharmacologic bridge to transplantation. The findings also suggest that milrinone as primary inodilator therapy may be associated with less need for mechanical ventricular support.

Postmortem MR imaging of the brains of patients with AIDS.

Forty-two postmortem formalin-fixed brains of known patients with AIDS were examined with T2-weighted MR imaging before brain cutting. The gross and microscopic brain findings were correlated with the T2 signal changes in the postmortem MR imaging. The brains included examples of progressive multifocal leukoencephalopathy with involvement of the central brain and cerebellum. The authors also encountered the coexistence of progressive multifocal leukoencephalopathy and HIV encephalitis, and the T2 signal changes for each were compared. The T2 signal changes of leptomeningeal and perivascular space cryptococcal infection and CMV ependymitis are documented. Several expressions of primary cerebral lymphoma, including large nodules, choroid plexus infiltration, and diffuse microscopic sites of tumor also are assessed.

Impaired beta 2-adrenergic agonist-induced venodilation in Indians of Asian origin.

OBJECTIVES: Vascular responsiveness to infusions of vasoactive substances varies between ethnic groups. Indians of Asian origin are a rapidly growing ethnic group in the United States but have not been extensively studied. We sought to determine whether there was any difference in venous responsiveness to a local infusion of vasoactive substances between Indians of Asian origin and white subjects. METHODS: We used the dorsal hand vein compliance technique to construct full dose-response curves to the beta 2-agonist isoproterenol (2 to 270 ng/min) in hand veins preconstricted with phenylephrine in 11 young white subjects and in 11 young Asian Indian subjects. In addition, six subjects in each group were randomly selected to have full dose-response curves to nitroglycerin (0.006 to 1485 ng/min) generated. RESULTS: The maximal response (E(max)) to isoproterenol was smaller in Asian Indians (33.9% +/- 41.1% in Asian Indians versus 107.0% +/- 60.1% in white subjects; p < 0.01). There was no difference in the log of the dose that produced half-maximal venodilation [log(ED50)] between the two groups (1.10 +/- 0.57 in Asian Indians versus 1.15 +/- 0.50 in white subjects). However, nitroglycerin infusion produced similar responses for both the E(max) and the log(ED50) between the two groups. CONCLUSION: These results indicate that differences may exist in beta-adrenergic responsiveness among white subjects and Indians of Asian origin. Therapy for diseases that use beta-adrenergic responses, such as hypertension, must take into account these differential vascular responses because they may affect their efficacy in Asian Indians.

Phosphorylation of interphotoreceptor retinoid-binding protein (IRBP).

The phosphorylation of interphotoreceptor retinoid-binding protein (IRBP), the major soluble (glycolipo) protein of the interphotoreceptor matrix (IPM) and a putative intercellular retinoid-transport vechicle, has been examined in a crude bovine IPM wash using [?-(32)P]ATP. SDS-polyacrylamide gel electrophoresis and autoradiography, size-exclusion high-performance liquid chromatography (HPLC) and ion-exchange HPLC all showed IRBP to be phosphorylated in this system. The phosphorylation probably is of serine and/or threonine residues rather than of tyrosine. Interestingly, phosphorylated IRBP was bound tightly to concanvalin A (Con A)-Sepharose and was not eluted by 50 mM ?-methyl-d-mannoside indicating a marked alteration in binding characteristics upon phosphorylation.

Phorbol ester- and light-induced endogenous phosphorylation of rat rod outer-segment proteins.

We have previously described the presence of a C-kinase in bovine retinal rod outer segments (ROS) (Kapoor and Chader, 1984). In this study, we have labeled rat retinas with freshly neutralized radiolabeled sodium phosphate (32P or 33P) by intravitreal injection and compared the phosphorylation patterns of ROS proteins induced by light and specific activators of the C-kinase phosphorylation system. Except for light treatment, all procedures were carried out in complete darkness using an infrared image converter. Incubation of 33P-labeled retinas in light for 5 min resulted in the phosphorylation of rhodopsin, 80-, 65-, 47-, 44-, and 15,000 MW proteins of crude ROS. Incubation of 33P-labeled retinas with 0.5 microM 12-O-tetradecanoylphorbol-13-acetate (TPA) resulted in the phosphorylation of several proteins including those at 80-, 65-, 47-, 44-, and 15,000 MW in crude ROS. ROS prepared in complete darkness did not exhibit any phosphorylation of proteins whereas ROS prepared in red light exhibited variable low phosphorylation of 80-, 47-, 44- and 15,000 MW proteins. 1-oleoyl-2-acetylglycerol (OAG) at 500 micrograms ml-1 caused the phosphorylation of the same proteins as observed with TPA. TPA (0.5-500 microM) and OAG (150-500 micrograms ml-1) did not induce rhodopsin phosphorylation. When purified ROS were prepared from 33P-pre-labeled retinas, the complete darkness control did not exhibit phosphorylation of any proteins. TPA, however, induced the phosphorylation of 80- and 65,000 MW proteins and light induced the phosphorylation of 80-, 65,000 MW proteins as well as opsin monomer and dimer. Affinity chromatography of phosphorylated ROS proteins on con A-Sepharose revealed that TPA does not induce rhodopsin phosphorylation whereas light does. Since light and TPA induced the phosphorylation of 80- and 65,000 MW proteins in ROS, it is possible to suggest at least a partial linkage of light- and C-kinase-mediated effects in situ.

Distribution of the regulatory subunit of type II cAMP-dependent protein kinase in Y-79 retinoblastoma cells. Effect of butyrate.

An indirect immunofluorescence technique was employed to determine the intracellular distribution of the regulatory subunit of type II cyclic adenosine 3':5'-monophosphate-dependent protein kinase (RII) in Y-79 human retinoblastoma cells growing in monolayer culture. During the initial phases of growth (6 hr-6 days after seeding), RII was confined to the cytoplasmic areas of the Y-79 cells, seemingly, the Golgi apparatus. Treatment of cells for 3-5 days with 4 mM butyrate resulted in translocation of RII from cytoplasm to nuclei (mainly nucleoli) of cells. In a later stage of growth (24-day-old cultures), RII immunofluorescence was significantly decreased in all compartments within the untreated cells. In contrast, about 70% of the butyrate-treated cells yet showed nucleoli and/or cytoplasmic localization of RII at this stage. The nucleolar appearance of RII was parallel to the growth arrest and differentiation induced by butyrate.

Extracellular localization of cyclic GMP in the house cricket male accessory reproductive gland and its fate in mating.

The male accessory reproductive gland (ARG) of the house cricket, Acheta domesticus (L.), contains an exceedingly high concentration of cyclic GMP, about 1,000 pmol/mg protein. Immunofluorescent localization and radioimmunoassay measurements show that cyclic GMP is concentrated in a small number of tubules. It accumulates in the tubule lumina where it is protected from degradation by phosphodiesterases. Cyclic GMP is secreted by the ARG and is incorporated into spermatophores. Over 80% of spermatophore cyclic GMP is found in the handle-capillary tube, a thin conduit through which sperm pass during transfer to the female. The concentration of cyclic GMP in the insemination fluid is about 20 microM but does not appear to be specifically associated with the sperm. Cyclic GMP enters the female spermatheca during insemination but disappears rapidly. Physiological effects of cyclic GMP on sperm were not observed nor was an effect of cyclic GMP observed on egg laying by mated females. Cyclic AMP was localized on sperm flagella in the spermatophore and in the spermatheca. These studies indicate that cyclic nucleotides have important roles in insect reproduction and that the house cricket is a good model for elucidating these functions.

Extracellular cGMP phosphodiesterase related to the rod outer segment phosphodiesterase isolated from bovine and monkey retinas.

A phosphodiesterase (PDE) has been characterized in the interphotoreceptor matrix (IPM) of light-adapted fresh bovine retinas. It is obtained through a gentle rinsing of the retinal surface under conditions where the light-activated rod outer segment (ROS) enzyme remains attached. The enzyme has an apparent native molecular weight of 350 000 by gel filtration and appears as a doublet at Mr 47 000 and 45 000 on sodium dodecyl sulfate-polyacrylamide gels. It has an apparent Km value for cGMP of 33 microM and an apparent Km value for cAMP of 2200 microM. It is activated 3-6-fold by protamine and over 40-fold by trypsin. Protamine has no effect on the Km for cGMP while trypsin decreases the Km for cGMP by a factor of 2. The enzyme occurs in at least two forms as evidenced by two distinct peaks of activity after gel electrophoresis under nondenaturing conditions. A heat-stable inhibitor is tightly bound to the enzyme. The inhibitor obtained from the IPM PDE inhibits 98% of the activity of the trypsin-activated ROS PDE: conversely, the inhibitor obtained by boiling the ROS PDE completely inhibits the trypsin-activated IPM enzyme. A high-affinity monoclonal antibody to the active site of the ROS PDE, ROS 1 [Hurwitz, R., Bunt-Milan, A.H., & Beavo, J. (1984) J. Biol. Chem. 259, 8612-8618], quantitatively absorbs the IPM PDE. These observations indicate a clear relationship between these two PDEs even though their location, sizes, and specific functions in the retina appear to be distinct.

Alteration in gene expression at the onset of human Y-79 retinoblastoma cell differentiation.

We have tested the hypothesis that differentiation and growth arrest of Y-79 human retinoblastoma cells in culture is associated with a modification of gene expression. We first examined proteins translated from mRNAs isolated from Y-79 cells growing in suspension and in attachment cultures in serum-containing medium and found them to be markedly different. This suggests that membrane-substrate interactions are of major consequence in the biochemical differentiation of these cells. Secondly, we examined the patterns of proteins translated from attached cells which had been induced to morphologically differentiate into neuronal-like and glial-like cells by serum-withdrawal and dibutyryl cAMP treatment respectively. The in vitro translatable proteins of mRNAs isolated from these cultures were found to be markedly different from those of the suspension and attachment cultures. Thirdly, we found that treatment of cells growing in attachment culture in serum-containing medium supplemented with 8-bromo cAMP, butyrate and retinoic acid as well as dibutyryl cAMP resulted in discreet alterations in proteins translated in vitro from extracted mRNAs. Although all these substances inhibit the growth of Y-79 cells, only dibutyryl cAMP and butyrate result in morphological differentiation of cells. Our results suggest that (1) attachment and morphological differentiation of Y-79 cells are both related to specific alterations in gene expression and (2) differentiation and inhibition of cell growth by various agents can be correlated with changes in translatable mRNA species although all agents do not act in the same mode.

Endogenous phosphorylation of retinal photoreceptor outer segment proteins by calcium phospholipid-dependent protein kinase.

A calcium phospholipid-dependent protein kinase (C-kinase) activity was detected in the soluble fraction of rod outer segments (ROS) of the bovine retina. The enzyme required calcium, phosphatidylserine (PS) and diacylglycerol for maximal activity. In the presence of calcium and PS, C-kinase endogenously phosphorylated proteins with molecular weights of 95,000, 91,000, 31,000, 21,000, 19,000, 18,000, 16,000, 14,000 and 11,000. Addition of diolein in the reaction mixture further enhanced the endogenous phosphorylation of these proteins. Retinal was found to inhibit the phosphorylation of endogenous proteins by C-kinase in a concentration dependent manner. Half-maximal inhibition of enzyme activity was obtained at a retinal concentration of about 12 microM. These results suggest that calcium, phospholipids and the C-kinase enzyme may play an important role in the functional regulation of rod photoreceptors and, with retinal, perhaps in the visual process as well.

Nucleolar accumulation of cyclic adenosine 3':5'-monophosphate receptor proteins during regression of MCF-7 human breast tumor.

Cyclic adenosine 3':5'-monophosphate (cAMP) receptor proteins (high-affinity binding proteins) present in growing and regressing MCF-7 human breast tumors were identified and characterized by the use of the photoaffinity-labeled 8-azido[32P]-cAMP and the affinity-purified antibodies to type I and type II regulatory subunits (RI and RII, respectively) of cAMP-dependent protein kinase. The cytosol fraction of growing MCF-7 tumors contained four major types of the 8-azido[32P]cAMP-binding proteins with molecular weights of 35,000, 47,000, 50,000, and 52,000. Following estrogen withdrawal, the amount of these proteins increased in the cytosol of regressing tumors. RI antibody immunoprecipitated cAMP receptor protein with a molecular weight of 47,000, whereas RII antibody immunoprecipitated Mr 50,000 and 52,000 proteins. The Mr 35,000 protein was not precipitated by either RI or RII antibodies. In the nuclear extracts of the growing tumors, the 8-azido-[32P]cAMP-binding proteins with molecular weights of 34,000, 35,000, 44,000, and 47,000 were detected. Following estrogen withdrawal, the 8-azido[32P]cAMP-binding proteins with molecular weights of 50,000 and 52,000 newly appeared in the nuclei of regressing tumors. The Mr 47,000 protein was immunoprecipitated by RI antibody and the Mr 34,000, 44,000, 50,000, and 52,000 proteins were precipitated by RII antibody. An indirect immunofluorescence revealed that, during regression of MCF-7 tumors, the intensity of immunofluorescence of RII proteins dramatically increased in the nucleoli, whereas immunofluorescence of RI remained the same in the nuclei. These results suggest that, during hormone-induced regression of human breast tumors, the Mr 50,000 and Mr 52,000 RII cAMP-binding proteins are translocated to the nucleoli from cytoplasm. Thus, the accumulation of these cAMP receptor proteins at nucleolar site(s) correlates with the regression of MCF-7 tumors.

Appearance of 50,000- and 52,000-dalton cAMP receptor proteins in the nucleoli of regressing MCF-7 human breast cancer upon estrogen withdrawal.

Affinity purified antibodies to type I and type II regulatory subunits (RI and RII, respectively) of cAMP-dependent protein kinase were utilized to identify and localize the cAMP receptor proteins in growing vs regressing MCF-7 tumors in nude mice. In the nuclear extracts of growing tumors the RI antibody immunoprecipitated cAMP receptor protein of 47,000 daltons, whereas the RII antibody precipitated 44,000- and 34,000-dalton cAMP receptor proteins. Following estrogen withdrawal, new species of cAMP receptor proteins with molecular weights of 50,000 and 52,000 appeared in the nuclei of regressing tumors. The 50,000- and 52,000-dalton proteins were specifically precipitated by the RII antibody but not by RI antibody. Indirect immunofluorescence revealed that during regression of MCF-7 tumors, the intensity of immunofluorescence of RII antibody crossreacting cAMP binding proteins dramatically increased in the nucleoli whereas the immunofluorescence of RI remained the same. These results suggest a regulatory role of RII in mammary cancer regression.