Tissue distribution and mode of DNA methylation in mice by methyl methanesulphonate and N-methyl-N' -nitro-N-nitrosoguanidine: lack of thymic lymphoma induction and low extent of methylation of target tissue DNA at 0-6 of guanine.

The methylating agents methyl methanesulphonate (MMS) and N-methyl N'-nitro-N-nitrosoguanidine (MNNG), administered by single i.p. injection in mice failed to yield thymic lymphoma at doses around 60% of the LD50 values, in contrast to MNUA which gives a high yield of tumours by this route. Comparison of the tissue distribution and mode of DNA methylation by these agents showed a positive correlation with ability to methylate the 0-6 atom of guanine in DNA of the target tissues thymus and bone marrow and tumorigeneis. MMS gave a low yield of this product due to its relatively low Sn1 reactivity but was able to methylate DNA extensively at other sites in the target tissues and other organs examined. MNNG despite its ability to methylate 0-6 of guanine in DNA in vitro to the same relative extent as the potent carcinogen MNUA, methylated DNA of thymus and bone marrow to a very small extent in vivo but was able to methylate DNA in certain other tissues nearer the site of i.p. injection. These findings contrast with the general relatively extensive methylation of 0-6 of guanine in DNA of the target tissues and other organs by N-methyl-N-nitrosourea (MNUA).     

Genetic toxicity of six carcinogens and six non-carcinogens in the Drosophila wing spot test

Six rodent carcinogens, 5 of which are also human carcinogens, and 6 compounds recognized as non-carcinogens were tested for their genotoxic activity in the Drosophila melanogaster wing spot test. 72-h-old larvae trans-heterozygous for the recessive wing cell markers 'multiple wing hairs' (mwh) and 'flare' (flr3) were fed various concentrations of the test compounds for a period of 48 h. With amitrole and 4-aminobiphenyl, larvae of the same age were also given an acute treatment of 6 h with higher concentrations, and, in addition, 48-h-old larvae were fed for a longer period of 72 h. Repeats of all experiments document the good reproducibility of the results in the wing spot test. Amitrole and 4-aminobiphenyl were genotoxic after both 48-h and 72-h treatments, but their activity could not be detected following acute exposure of only 6 h. Chlorambucil and melphalan were clearly genotoxic. The carcinogens sodium arsenite and sodium arsenate, however, which are highly toxic to Drosophila, could only be tested at low exposure levels and were negative under these treatment conditions. The 6 non-carcinogens (ascorbic acid, 2-aminobiphenyl, mannitol, piperonyl butoxide, stannous chloride and titanium dioxide) were all definitely non-genotoxic in the Drosophila wing spot test. The data for the non-carcinogens demonstrate that non-genotoxic compounds can be identified in the wing spot test with a reasonable experimental effort.     

On the mechanism of peroxyoxalate chemiluminescence. Quenched chemiluminescence as a detection method in HPLC

Several analytes such as the inorganic anions bromide, iodide, sulphite and nitrite and organic compounds as substituted anilines and sulphur compounds cause quenching of peroxyoxalate chemiluminescence. A detection method for liquid chromatography based on the quenching phenomenon has been developed. It makes use of an immobilized luminophore, i.e. 3-aminofluoranthene covalently bound via an alkyl-spacer on controlled pore glass, packed in the detector cell. The mechanism behind the quenching has been elucidated by investigating the roles of luminophores (both in the liquid and in solid state) and oxalates in peroxylate CL with respect to quenchers. Most probably the quencher destroys the radical ion pair produced after electron transfer in the last stage of the CIEEL reaction scheme, thus preventing the formation of electronically excited luminophore.     

Ca release from mitochondria induced by prooxidants

A variety of chemically different prooxidants causes Ca²⁺ release from mitochondria. The prooxidant-induced Ca²⁺ release occurs from intact mitochondria via a route which is physiologically relevant and may be regulated by protein ADP-ribosylation. When the released Ca²⁺ is excessively cycled by mitochondria they are damaged. This leads to uncoupling, a decreased ATP supply, and a decreased ability of mitochondria to retain Ca²⁺. Excessive Ca²⁺ cycling by mitochondria will deprive cells of ATP. As a result, Ca²⁺ ATPases of the endoplasmic (sarcoplasmic) reticulum and the plasma membrane are stopped. The rising cytosolic Ca²⁺ level cannot be counterbalanced due to damage of mitochondria which, under normoxic conditions, act as safety device against increased cytosolic Ca²⁺. It is proposed that prooxidants are toxic because they impair the ability of mitochondria to retain Ca²⁺.     

One Step Isolation of Bovine Asialoglycoprotein Receptor and Its Characterization by Sequence Analysis and MALDI Mass Spectrometry

The asialoglycoprotein receptor (ASGP-R), which is responsible for the uptake of partially deglycosylated serum glycoproteins was isolated from bovine liver. The receptor was purified in one step from solubilized plasma membranes by affinity chromatography on 6-(-D-lactosyl)-n-hexylamine coupled to N-hydroxysuccinimide activated Sepharose with a coupling degree of 7.6 mol/ml gel. The preparation yielded two distinct polypeptides with apparent molecular weights of 48 and 43 kDa as determined by sodium dodecyl sulfatepolyacrylamide gel electrophoresis. A polyclonal antibody raised against the human ASGP-R recognized the bovine 43 kDa protein in Western blot analysis. The 48 and 43 kDa polypeptides were digested by trypsin and the digests were subsequently analyzed by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. Sequence analysis of four tryptic fragments, two each of the 48 kDa and of the 43 kDa polypeptides revealed that these were highly homologous to ASGP-R subunits from man, mouse and rat.     

Comparative Value of Four Measures of Retention in Expert Care in Predicting Clinical Outcomes and Health Care Utilization in HIV Patients

This study compared the ability of four measures of patient retention in HIV expert care to predict clinical outcomes. This retrospective study examined Veterans Health Administration (VHA) beneficiaries with HIV (ICD-9-CM codes 042 or V08) receiving expert care (defined as HIV-1 RNA viral load and CD4 cell count tests occurring within one week of each other) at VHA facilities from October 1, 2006, to September 30, 2008. Patients were ≥18 years old and continuous VHA users for at least 24 months after entry into expert care. Retention measures included: Annual Appointments (≥2 appointments annually at least 60 days apart), Missed Appointments (missed ≥25% of appointments), Infrequent Appointments (>6 months without an appointment), and Missed or Infrequent Appointments (missed ≥25% of appointments or >6 months without an appointment). Multivariable nominal logistic regression models were used to determine associations between retention measures and outcomes. Overall, 8,845 patients met study criteria. At baseline, 64% of patients were virologically suppressed and 37% had a CD4 cell count >500 cells/mm³. At 24 months, 82% were virologically suppressed and 46% had a CD4 cell count >500 cells/mm³. During follow-up, 13% progressed to AIDS, 48% visited the emergency department (ED), 28% were hospitalized, and 0.3% died. All four retention measures were associated with virologic suppression and antiretroviral therapy initiation at 24 months follow-up. Annual Appointments correlated positively with CD4 cell count >500 cells/mm³. Missed Appointments was predictive of all primary and secondary outcomes, including CD4 cell count ≤500 cells/mm³, progression to AIDS, ED visit, and hospitalization. Missed Appointments was the only measure to predict all primary and secondary outcomes. This finding could be useful to health care providers and public health organizations as they seek ways to optimize the health of HIV patients.