p63 deficiency activates a program of cellular senescence and leads to accelerated aging

The p53 tumor suppressor plays a key role in organismal aging. A cellular mechanism postulated to drive the aging process is cellular senescence, mediated in part by p53. Although senescent cells accumulate in elderly individuals, most studies have relied on correlating in vitro senescence assays with in vivo phenotypes of aging. Here, using two different mouse models in which the p53-related protein p63 is compromised, we demonstrate that cellular senescence and organismal aging are intimately linked and that these processes are mediated by p63 loss. We found that p63(+/-) mice have a shortened life span and display features of accelerated aging. Both germline and somatically induced p63 deficiency activates widespread cellular senescence with enhanced expression of senescent markers SA-beta-gal, PML, and p16(INK4a). Using an inducible tissue-specific p63 conditional model, we further show that p63 deficiency induces cellular senescence and causes accelerated aging phenotypes in the adult. Our results thus suggest a causative link between cellular senescence and aging in vivo, and demonstrate that p63 deficiency accelerates this process.     

Structure and expression of the gene for Pv200, a major blood-stage surface antigen of Plasmodium vivax.

Molecular cloning and structure analysis of the gene encoding the Pv200 protein of the Sal-1 strain of Plasmodium vivax revealed an overall identity of 34–37% when the deduced amino acid sequence was compared with the sequences of various major merozoite surface antigens of Plasmodium falciparum, Plasmodium yoelii and Plasmodium chabaudi. When the Sal-1 Pv200 sequence was compared with the corresponding sequence from the Belèm strain of P. vivax, it was found that the two merozoite surface antigens were relatively well conserved with an overall amino acid sequence identity of 81%. A region of 23 repeated glutamine residues, found in the sequence of the Belèm isolate was not found, however, in the Sal-1 sequence. Amino-and carboxy-terminal domains of the Pv200 protein were expressed in the yeast Saccharomyces cerevisiae. Each recombinant protein was shown to react with antibodies in sera from splenectomized Bolivian Saimiri monkeys that had been infected previously with P. vivax, and in human sera from individuals with a history of exposure to vivax malaria. The availability of recombinant DNA-derived Pv200 proteins will now allow a full assessment of their utility in the diagnosis and immunoprophylaxis of the benign tertian malaria associated with P. vivax infection.     

The origin of human B and T cells from multipotent stem cells: a study of the Tn syndrome

The Tn (or polyagglutinability) syndrome corresponds to a human nonmalignant acquired condition which results from a somatic mutation occurring at the level of bone marrow stem cells. This model offers therefore a unique opportunity to study the contribution of multipotential stem cells to the maintenance of cells from the lymphoid lineage. We found that the Tn mutation is expressed by both myeloid and lymphoid mature blood cells. Whereas a large proportion of surface IgM-bearing B cells carry the Tn mutation, only a small percentage of T cells and IgA- or IgG-bearing B cells are defective, showing that under physiological conditions the penetration of stem cells into the various myeloid and lymphoid compartments is variable.     

Diagnosis of obstructive sleep apnea

The diagnosis of obstructive sleep apnea is frequently made by taking a meticulous history coupled with a high index of suspicion. Snoring and hypersomnolence are clinical features common to individuals with sleep apnea. Since snoring is said to be a “disease of listeners,” it is not uncommon that bed partners report an increased incidence of depression and marital displeasure. It is for this reason that the spouse or bed partner should be interviewed, since the patient may not be aware of any sleeping problems. Physicians should also be alert to complaints of excessive daytime somnolence, because studies have shown that patients with obstructive sleep apnea are at increased risk for automobile crashes (41, 42). It has been estimated that approx 58, 000 motor vehicle accidents involving people with sleep apnea will occur in the US each yr (43). By proper diagnosis and treatment, the physician is in a unique position to prevent at least some of the automobile accidents that result from falling asleep while driving. Polysomnography is the only definitive way to obtain a diagnosis of sleep apnea. This allows the physician not only to diagnosis the disorder, but also helps in the evaluation of the severity of the syndrome and selection of therapy. An ENT evaluation is also important in ruling out anatomic disorders that can cause upper airway obstruction. Certain factors, such as alcohol and sedative ingestion, may aggravate the condition in a person predisposed to sleep apnea, and subtle changes, such as unexplained hypertension, polycythemia, and cor pulmona!e, should lead one to investigate the possibility of sleep apnea as the etiology.     

Lethal hyperkinetic ventricular arrhythmias and echocardiographic findings in patients with arrhythmogenic right ventricular disease

Posters

Lethal hyperkinetic ventricular arrhythmias and echocardiographic findings in patients with arrhythmogenic right ventricular disease     

Chromosome aberration induction in Chinese hamster ovary cells by restriction enzymes with different methylation sensitivity

The isoschizomer pair MspI and HpaII were used to investigate whether the putative specificity of restriction endonucleases would be maintained when they were introduced into mammalian cells. Although both enzymes recognize the sequence CCGG, HpaII will cut only if the internal cytosine is unmethylated, whereas MspI will cut regardless of the methylation status. Cleavage results in a cohesive-end DNA double-strand break, which can lead to the formation of chromosome aberrations. Since mammalian DNA is heavily methylated, one would expect MspI to be much more effective than HpaII at inducing chromosome aberrations in Chinese hamster ovary cells. In fact, during G₁, MspI induced a >90-fold higher number of aberrations than did HpaII. Cell cycle studies indicated that during early S there was a 30-fold increase in HpaII-induced aberrations. This increase may be due to increased accessibility of replicating hypomethylated DNA. Cells that were treated with the demethylating agent 5-aza-2-deoxycytidine (AzdC) displayed only a moderate increase in HpaII-induced aberrations during G₁. This observation, together with the results of restriction enzyme analysis of genomic DNA, indicated that demethylation was incomplete. The effects of AzdC on the induction of aberrations by MspI suggested that AzdC increases chromatin accessibility. Our results were consistent with the expected specificity of MspI and HpaII. Thus, it appears that restriction endonucleases can play a useful role in determining the biological consequences of DNA double-strand breaks.     

Generalized pharmacokinetic modeling for drugs with nonlinear binding: I. Theoretical framework

The following integrodifferential equation is proposed as the basis for a generalized treatment of pharmacokinetic systems in which nonlinear binding occurs $$\phi '(c_u )c'_u = - q(c_u ) + g*c_u + f$$ where c_u≡unbound plasma drug concentration, f≡drug input rate,'indicates the derivative of a function, and * indicates the convolution operation: (g* c_u)(t)=∫ ₀ ^t g(t?u)c_udu.Possible physical interpretations of the functions q, g and f are: q (c_u)≡ rate at which drug leaves the sampling compartment, g * c_u ≡ rate at which drug returns to the sampling compartment from the peripheral system (tissues that are kinetically distinct from the sampling compartment), and φ(c_u) ≡ amount of drug in the sampling compartment. The approach assumes that drug binding is sufficiently rapid that it may be treated as an equilibrium process. It may be applied to systems in which nonlinear binding occurs within the sampling compartment, i.e., in the systemic circulation or in tissues to which drug is rapidly distributed. The proposed relationship is a generalization of most existing models for drugs with nonlinear binding. It can serve as a general theoretical framework for such models or as the basis for “model-independent” methods for analyzing the pharmacokinetics of drugs with nonlinear binding. Computer programs for the numerical solution of the integrodifferential equation are presented. Methods for pharmacokinetic system characterization, prediction and bioavailability are presented and demonstrated.     

Glutamate: its role in learning,memory, and the aging brain

l-Glutamate is the most abundant of a group of endogenous amino acids in the mammalian central nervous system which presumably function as excitatory neurotransmitters and under abnormal conditions may behave as neurotoxins. As neurotransmitters, these compounds are thought to play an important role in functions of learning and memory. As neurotoxins, they are believed to be involved in the pathogenesis of a variety of neurodegenerative disorders in which cognition is impaired. Moreover, brain structures which are considered anatomical substrata for learning and memory may be particularly vulnerable to the neurotoxic actions of these excitatory amino acids, especially in the elderly who are also the segment of the population most susceptible to impairments of mnemonic function. This paper is a review of data concerning the role of excitatory amino acids in the processes of learning and memory and in the pathogenesis and treatment of disorders thereof.     

Modulation of drug cytotoxicity in wild-type and multidrug-resistant tumor cells by stereoisomeric series of C-20′-vinblastine congeners that lack antimicrotubule activity

Summary Seven binary vinca alkaloid congeners were newly synthesized as the C14 or C16(20) or C1416(20) stereoisomers of C20-modified VBL. These congeners lacked detectable antimicrotubule activity in assays of polymerization of purified microtubule protein and of mitotic arrest induction. The compounds modulated the cytotoxicity of VBL, VCR, and DOX in sarcoma and colontumor cell lines. In wild-type cell lines, each congener elicited a concentration-dependent enhancement of cytotoxicity that was drug-and cell-type-selective. For example, C20-deoxy C141620-epi VBL sensitized sarcoma S180 cells 19-fold to DOX and 11-fold to VCR but had no effect on VBL cytotoxicity. In the rat colon-cancer cell lines there was preferential enhancement of VCR cytotoxicity by most congeners. In two MDR cell strains of S180, the modulation potency of each congener was independent of specific drug or of resistance level. As a result, the amount of modulator (concentration) required for reversal was proportional to the drug-resistance level. Such properties were not displayed by the monomeric vinca alkaloid modulator vindoline. The potency of drug modulation in both wild-type and MDR cell strains was dependent on the stereoisomeric form of the congener and its C20-substituents.Abbreviations MDR multidrug resistance - VBL vinblastine - VCR vincristine - DOX doxorubicin - MTP purified microtubule protein - MTX methotrexate - 5-FU 5-fluorouracil This work was supported by grants CH-424 from the American Cancer Institute (to L.S.B.), RO1 12010 from the NCI (to M.E.K.), and P30 CA 22435 from the NCI (to the Vermont Regional Cancer Center). The contents are the responsibility of the authors and do not necessarily represent the views of the NCI     

Aortocaval compression in the sitting and lateral decubitus positions during extradural catheter placement in the parturient

We prospectively studied the incidence of concealed aortocaval compression in parturients at term during identification of the extradural space. Forty ASA I or II parturients, at term and in active labour, who requested extradural analgesia were randomly allocated to one of two groups. Parturients in the first group (n = 22) were positioned in the left lateral decubitus position and those in the second group (n = 18) were in the sitting position. Cardiac output (CO) was recorded at one-minute intervals for five minutes before extradural catheter placement (supine position with a 15° wedge under the right side), and during and thereafter for five minutes (in the supine wedged position), using the BoMED NCCOM3-R7 thoracic electrical bioimpedance (TEB) monitor. The average of five CO_TEB recordings before positioning the patient were compared with the average of five CO_TEB measurements during and after extradural space identification. A change of >25% CO_TEB was considered beyond machine variability. Upper limb arterial pressure was recorded at one-minute intervals. In the left lateral decubitus position, 17 of 22 patients demonstrated a >25% reduction in CO_TEB compared with five of 18 patients in the sitting position (X²,P <0.01). The percentage change in CO_TEB in the lateral decubitus position (?29.8%, 95% CI ?17% to ?44%) was greater than the sitting position (?9.8%, 95% CI +36% to ?32%) (P <0.01). A decreased incidence of aortocaval compression during identification of the extradural space was demonstrated in the sitting position when compared with the left lateral decubitus position.