Histone H1 reduces the frequency of initiation in Xenopus egg extract by limiting the assembly of prereplication complexes on sperm chromatin

Somatic histone H1 reduces both the rate and extent of DNA replication in Xenopus egg extract. We show here that H1 inhibits replication directly by reducing the number of replication forks, but not the rate of fork progression, in Xenopus sperm nuclei. Density substitution experiments demonstrate that those forks that are active in H1 nuclei elongate to form large tracts of fully replicated DNA, indicating that inhibition is due to a reduction in the frequency of initiation and not the rate or extent of elongation. The observation that H1 dramatically reduces the number of replication foci in sperm nuclei supports this view. The establishment of replication competent DNA in egg extract requires the assembly of prereplication complexes (pre-RCs) on sperm chromatin. H1 reduces binding of the pre-RC proteins, XOrc2, XCdc6, and XMcm3, to chromatin. Replication competence can be restored in these nuclei, however, only under conditions that promote the loss of H1 from chromatin and licensing of the DNA. Thus, H1 inhibits replication in egg extract by preventing the assembly of pre-RCs on sperm chromatin, thereby reducing the frequency of initiation. These data raise the interesting possibility that H1 plays a role in regulating replication origin use during Xenopus development.     

Cytotoxicity and tolerance to DNA adducts of alicyclic mixed amine platinum(II) homologs in tumor models sensitive and resistant to cisplatin or tetraplatin

Structure-cytotoxicity relationships for six alicyclic cis-(NH3)(R-NH2)Cl2Pt(II) complexes, where R=C3H5, C4H7, C5H9, C6H11, C7H13 and C8H15 (complexes abbreviated C3, C4, C5, C6, C7 and C8, respectively), were evaluated against four sensitive (L1210/0, A2780, FSaIIC and Colon 26), two cisplatin-resistant (L1210/DDP and 2780CP) and two tetraplatin-resistant (L1210/DACH and 2780TP) murine and human tumor cell lines. The studies demonstrated that in general the structure of C6 was optimal within the homologous series for cytotoxic potency against these tumor models. Biochemical pharmacologic studies indicated that the greater sensitivity of cells to C6 could be correlated with their low tolerance to DNA damage induced by this homolog. These results provide evidence for the alicyclic ring size as a structural determinant of DNA damage tolerance and anti-tumor activity in sensitive and resistant tumor cells.     

Inhibition of diabetic nephropathy by a GH antagonist: a molecular analysis

Streptozotocin-treated C57B1/SJL mice developed glomerular hypertrophy and light microscopic lesions mimicking human diabetic glomerulosclerosis. In contrast, there were no glomerular hypertrophy and lesions in diabetic mice transgenic (TG) for a mutated growth hormone (bGH-G119K) that competes with native endogenous GH and results in dwarfism. We examined the molecular events underlying these findings. The non-transgenic (non-TG) diabetic mouse glomeruli had an increase in mRNA coding for alpha 1IV collagen, laminin B1, TGF-beta 1, 72 kDa collagenase, and TIMP-3. In contrast, glomerular type IV collagen and laminin B1 mRNA levels were normal in diabetic TG dwarf mice. However, the 72 kDa gelatinase, TIMP-3, and TGF-beta 1 mRNAs were elevated in the diabetic dwarfs. Type IV collagen and laminin accumulated in the glomeruli of diabetic non-TG, but not of diabetic dwarf mice, by immunofluorescence microscopy, confirming the mRNA data. GH binding protein mRNA levels were comparable in glomeruli from dwarf and non-TG mice, both diabetic and non-diabetic. We did not detect GH receptor mRNA in glomeruli. These data suggest that diabetic glomerulosclerosis is associated with an increase in type IV collagen and laminin synthesis, and that these changes do not occur in mice transgenic for bGH119K, a functional antagonist of GH. The increase of 72 kDa gelatinase, TIMP-3 and TGF-beta 1 mRNAs, independent of GH, suggested that these changes induced by hyperglycemia were not sufficient for the induction of glomerulosclerosis.     

Role of CD28/B7 co-stimulation in airway T helper 2 (TH2) immune responses in asthma

5'-Deoxy-5'-fluoro-O4-methylthymidine was synthesized by the reaction of the corresponding 5'-O-tosylate with KF in the presence of Kryptofix [222] and coupled to a 5'-phosphoramidite-activated CPG-bound oligodeoxynucleotide. The sequence of reactions and purifications were accomplished within 4 h, a necessary condition of the development of radiofluorinated antisense oligodeoxynucleotide probe for use with PET.     

Epidemiologic paradox in multiple births among Asians in Illinois. Correlation between risk factors and outcomes

OBJECTIVE: To determine if the plural birth rate, maternal risk factors and neonatal outcomes among Asian American populations residing in Illinois are homogeneous or heterogeneous with regard to maternal risk factors and neonatal outcomes and to attempt to establish correlations between maternal risk factors and neonatal outcomes. STUDY DESIGN: A total of 1,145,962 computerized birth certificate files were analyzed for 11 Asian subgroups giving birth in Illinois in the years 1989-1994. RESULTS: The multiple birth rates varied between 6 per 1,000 (Vietnamese) to 15 per 1,000 (Cambodian) (heterogeneity among all groups, P < .005). The percent of neonates born at gestational ages 22-33 weeks varied between 0 (Cambodian) to 28 (Thai). Japanese women showed the highest rate of neonates with birth weight less than 2,500 g after adjustment for race: 15.38 per 1,000. Women from Cambodia and Laos had the highest sum of maternal risk factors; those from the Philippines and Thailand had the least. The lowest collective adverse neonatal outcomes were in infants born to women from Cambodia and Laos. CONCLUSION: The 11 subgroups of Asians living in Illinois demonstrate heterogeneity with respect to multiple birth rate, selected maternal risk factors and adverse neonatal outcomes. After considering all maternal risk factors and neonatal outcomes, the two groups (Cambodians and Laotians) with the poorest maternal risk factors had the lowest rate of poor neonatal outcomes. This is the first time that this epidemiologic paradox has been observed in twins of Asian ancestry.     

Fat and Water Composition Affects Residual Catalatic Activity in Chicken Breast Heated to Specific End-point Temperatures

Fat and water contents of meat tissues strongly influence their thermo-physical properties. Seven groups of ground chicken breast meat containing varying amounts of fat and water were prepared for this investigation. Each group was heated to end-point temperatures (EPTs) of 69.0 to 71.0°C at 0.5°C intervals. Severity of heat treatments was evaluated by the total process lethality calculated using the General Method. The fat and water contents affected the heating time to reach specific EPTs and the residual catalatic activity at EPTs of 69.0, 69.5 and 70.0°C, but did not affect total process lethality. The variation of the catalase method for determining EPT was related to the sample composition.     

Exogenous and endogenous catecholamines inhibit the production of macrophage inflammatory protein (MIP) 1 alpha via a beta adrenoceptor mediated mechanism

Noradrenaline (NA) and adrenaline (Ad) are modulators of cytokine production. Here we investigated the role of these neurotransmitters in the regulation of macrophage inflammatory protein (MIP)-1alpha expression. Pretreatment of RAW 264.7 macrophages with NA or Ad decreased, in a concentration-dependent manner (1 nM-100 microM), MIP-1alpha release induced by bacterial lipopolysaccharide (LPS 10 ng ml(-1) LPS). The effect of NA was reversed by the selective beta-adrenoceptor antagonist propranolol (10 microM), but not by the alpha-adrenoceptor antagonist phentolamine (10 microM). In the concentration range of 10 nM-10 microM, isoproterenol, a beta-adrenoceptor agonist, but not phenylephrine (a selective alpha1-adrenoceptor agonist) or UK-14304 (a selective alpha2-adrenoceptor agonist) mimicked the inhibitory effects of catecholamines on MIP-1alpha production. Increases in intracellular cyclic adenosine monophosphate, elicited either by the selective type IV phosphodiesterase inhibitor rolipram (0.1 - 10 microM), or by prostaglandin E2, (10 nM-10 microM) decreased MIP-1alpha release, suggesting that increased cyclic AMP may contribute to the suppression of MIP-1alpha release by beta-adrenoceptor stimulation. Northern blot analysis demonstrated that NA (100 nM-10 microM), Ad, isoproterenol, as well as rolipram (100 nM-10 microM) decreased LPS-induced MIP-1alpha mRNA accumulation. NA and Ad (1-100 microM) also decreased MIP-1alpha production in thioglycollate-elicited murine peritoneal macrophages. Pretreatment of mice with either isoproterenol (10 mg kg(-1), i.p.) or rolipram (25 mg kg(-1), i.p.) decreased LPS-induced plasma levels of MIP-1alpha, while propranolol (10 mg kg(-1), i.p.) augmented the production of this chemokine, confirming the role of a beta-adrenoceptor mediated endogenous catecholamine action in the regulation of MIP-1alpha production in vivo. Thus, based on our data we conclude that catecholamines are important endogenous regulators of MIP-1alpha expression in inflammation.     

Migraine headache following stellate ganglion block for reflex sympathetic dystrophy

The alteration of extracranial blood flow in conjunction with clinical signs of autonomic nervous system dysfunction have led to various explanations concerning the pathophysiology of migraine headache. Reflex sympathetic dystrophy, a painful disorder of the sympathetic nervous system, can be treated by blocking the sympathetic nerves located in the stellate ganglion, resulting in vasodilation, ptosis, miosis, and anhydrosis. In theory, these changes could trigger a migraine headache attack secondary to autonomic dysfunction reflecting an imbalance between sympathetic and parasympathetic nervous systems. This may be especially true in a patient with a previous history of meningitis that may have resulted in a disorder of cerebrovascular regulation. We report a 56-year-old man with no previous history of migraine who developed migraine with aura after a stellate ganglion block. These episodic headaches occurred with decreasing frequency and severity for over 6 months, with eventual complete resolution. This interesting phenomenon has not been reported in the English literature and may help to better understand the pathophysiology of migraine.