Daily rhythm in pineal phosphodiesterase (PDE) activity reflects adrenergic/3',5'-cyclic adenosine 5'-monophosphate induction of the PDE4B2 variant

The pineal gland is a photoneuroendocrine transducer that influences circadian and circannual dynamics of many physiological functions via the daily rhythm in melatonin production and release. Melatonin synthesis is stimulated at night by a photoneural system through which pineal adenylate cyclase is adrenergically activated, resulting in an elevation of cAMP. cAMP enhances melatonin synthesis through actions on several elements of the biosynthetic pathway. cAMP degradation also appears to increase at night due to an increase in phosphodiesterase (PDE) activity, which peaks in the middle of the night. Here, it was found that this nocturnal increase in PDE activity results from an increase in the abundance of PDE4B2 mRNA (approximately 5-fold; doubling time, approximately 2 h). The resulting level is notably higher (>6-fold) than in all other tissues examined, none of which exhibit a robust daily rhythm. The increase in PDE4B2 mRNA is followed by increases in PDE4B2 protein and PDE4 enzyme activity. Results from in vivo and in vitro studies indicate that these changes are due to activation of adrenergic receptors and a cAMP-dependent protein kinase A mechanism. Inhibition of PDE4 activity during the late phase of adrenergic stimulation enhances cAMP and melatonin levels. The evidence that PDE4B2 plays a negative feedback role in adrenergic/cAMP signaling in the pineal gland provides the first proof that cAMP control of PDE4B2 is a physiologically relevant control mechanism in cAMP signaling.     

Melatonin modulates secretion of growth hormone and prolactin by trout pituitary glands and cells in culture

In Teleost fish, development, growth, and reproduction are influenced by the daily and seasonal variations of photoperiod and temperature. Early in vivo studies indicated the pineal gland mediates the effects of these external factors, most probably through the rhythmic production of melatonin. The present investigation was aimed at determining whether melatonin acts directly on the pituitary to control GH and prolactin (PRL) secretion in rainbow trout. We show that 2-[125I]-iodomelatonin, a melatonin analog, binds selectively to membrane preparations and tissue sections from trout pituitaries. The affinity was within the range of that found for the binding to brain microsomal preparations, but the number of binding sites was 20-fold less than in the brain. In culture, melatonin inhibited pituitary cAMP accumulation induced by forskolin, the adenyl cyclase stimulator. Forskolin also induced an increase in GH release, which was reduced in the presence of picomolar concentrations of melatonin. At higher concentrations, the effects of melatonin became stimulatory. In the absence of forskolin, melatonin induced a dose-dependent increase in GH release, and a dose-dependent decrease in PRL release. Melatonin effects were abolished upon addition of luzindole, a melatonin antagonist. Our results provide the first evidence that melatonin modulates GH and PRL secretion in Teleost fish pituitary. Melatonin effects on GH have never been reported in any vertebrate before. The effects result from a direct action of melatonin on pituitary cells. The complexity of the observed responses suggests several types of melatonin receptors might be involved.     

Combination of chemotherapy and gemtuzumab ozogamicin in adult Philadelphia positive acute lymphoblastic leukemia patient harboring CD33 expression

Gemtuzumab Ozogamicin (GO) is a humanized anti-CD33 antibody conjugated with a cytotoxic antitumor antibiotic, calicheamicin-g1. It was developed at the end of the nineties as 90% of the leukemic blast population of patients with acute myeloid leukaemia (AML) express the CD33 surface antigen (Dinndorf et al. [1] Blood 1986;67:1048-53). GO is currently approved in monotherapy for the treatment of CD33+ AML patients in first relapse, showing a 26% overall response rate and a median disease-free-survival of 5.2 months for responders (Larson et al. [2] Cancer 2005;104:1442-52). CD33 antigen expression is also observed at diagnosis (in 15% of cases) (Pui et al. [3] J Clin Oncol 1998;16:3768-73) or at relapse (Guglielmi et al. [4] Leukemia 1997; 11:1501-7) of acute lymphoblastic leukaemia (ALL), representing a potential cellular target for ALL patients. Case series have already demonstrated the efficacy of GO in children with relapsed CD33+ ALL with documentation of complete remission (CR) (Balduzzi et al. [5] Leukemia 2003;17:2247-8; Cotter et al. [6] Br J Haematol 2003;122:686-91; Zwaan et al. [7] Leukemia 2003;17:468-70). In the other hand, there is no report at our knowledge of the use of GO in the setting of adult CD33+ ALL patient. Here we report the case of a 30-year-old man with a refractory CD33+ ALL who received a salvage regimen combining chemotherapy + GO and achieved a transient CR.     

Intestinal obstruction associated with oral midodrine

Abstract. We report a case of severe ileus possibly related to midodrine. To our knowledge, this case report is the first one suggesting an inhibitory effect of midodrine on intestinal motility. The potential pharmacological mechanisms leading to this adverse drug reaction are discussed below.     

Lack of HIN-1 methylation defines specific breast tumor subtypes including medullary carcinoma of the breast and BRCA1-linked tumors

Medullary carcinoma is a poorly differentiated breast cancer with a high histologic grade and a paradoxically good prognosis. It accounts for only 3 percent of all breast cancers except in BRCA-1 families, in which it can account for as many as 13 percent of cancers. To date, only histologic criteria have been used to define this tumor type. In an attempt to more clearly define the genetic pathway leading to this subtype of cancer, we recently demonstrated that nearly 100 percent of these carcinomas display p53 mutations. In the present study, we extended our analysis to include HIN-1, a candidate tumor suppressor that has been shown to be silenced by methylation in the majority of breast tumors. In striking contrast to unselected sporadic invasive ductal carcinoma, we show that medullary carcinomas do not display a high frequency of HIN-1 methylation (p less than 0.001). This feature is also found in BRCA-1 associated tumors that shared several histologic characteristics with medullary carcinomas of the breast. Medullary carcinoma of the breast should therefore be considered to be a unique entity defined by specific histologic and molecular traits.     

Rapid and sensitive p53 alteration analysis in biopsies from lung cancer patients using a functional assay and a universal oligonucleotide array: a prospective study.

PURPOSE: Molecular profiling of alterations associated with lung cancer holds the promise to define clinical parameters such as response to treatment or survival. Because <5% of small cell lung cancers and <30% of non-small cell lung cancers are surgically resectable, molecular analysis will perforce rely on routinely available clinical samples such as biopsies. Identifying tumor mutations in such samples will require a sensitive and robust technology to overcome signal from excess amounts of normal DNA. EXPERIMENTAL DESIGN: p53 mutation status was assessed from the DNA and RNA of biopsies collected prospectively from 83 patients with lung cancer. Biopsies were obtained either by conventional bronchoscopy or computed tomography-guided percutaneous biopsy. Matched surgical specimens were available for 22 patients. Three assays were used: direct sequencing; a functional assay in yeast; and a newly developed PCR/ligase detection reaction/Universal DNA array assay. RESULTS: Using the functional assay, p53 mutation was found in 62% of biopsies and 64% of surgical specimens with a concordance of 80%. The sensitivity of the functional assay was determined to be 5%. Direct sequencing confirmed mutations in 92% of surgical specimens but in only 78% of biopsies. The DNA array confirmed 100% of mutations in both biopsies and surgical specimens. Using this newly developed DNA array, we demonstrate the feasibility of directly identifying p53 mutations in clinical samples containing <5% of tumor cells. CONCLUSIONS: The versatility and sensitivity of this new array assay should allow additional development of mutation profiling arrays that could be applied to biological samples with a low tumor cell content such as bronchial aspirates, bronchoalveolar lavage fluid, or serum.