The role of histones H3 and H1 in the formation of thymine-lysine cross-links during UV-irradiation of deoxyribonucleoprotein

The effect of UV light (lambda = 254 nm) on calf thymus DNP at low ionic strengths was studied. It was found that at the irradiation doses used the protein in the DNA-protein complex increases as the irradiation dose rises. Thermal treatment and acid hydrolysis resulted in a predominant release of histones H3 and H1 from the complex. Data from liquid high performance chromatography, amino acid analysis, thin-layer chromatography point to the induction by UV-light of a thymine-lysine bond, whose formation involves DNA thymines and histone lysine residues, predominantly H3 and H1 fractions.     

Chromosome studies in 952 infertile males with a sperm count below 10 million/ml

Summary A major chromosomal abnormality was observed in 10.3% of subfertile men in this study. This result is similar to a previous survey using the same criteria for selection of probands. The high frequency of chromosomal abnormalities emphasizes the importance of cytogenetic examination in subfertile men. The detection of such an abnormality should be followed by chromosome analysis in the patient's family. Prenatal diagnosis is indicated if a subfertile man with an abnormal karyotype fathers a child.     

Clinical importance of enteric communication with abdominal abscesses.

The dynamics of leucocytes in abdominal abscesses were studied using indium-111 autologous leucocyte scanning in 30 patients. Thirteen patients showing enteric drainage of leucocytes on delayed scans were characterised by a lack of abdominal localising signs and a low detection rate by ultrasound (25%). By contrast, 16 of 17 patients without enteric drainage had abdominal signs, and in these patients ultrasound was associated with a higher detection rate (58%). Despite the presence of an enteric route of drainage for the abscess 10 of the 13 patients needed surgical intervention. These results help explain the wide variation in clinical presentation of abdominal abscesses; suggest that 111In leucocyte scanning should be the initial investigation in those patients without focal signs; and show that formal surgical drainage is needed in patients recognised as having enteric communication with abscesses.     

Effect of nucleoside triphosphates on cyclic nucleotide phosphodiesterase: role of protein modulators

The effects of nucleoside triphosphates (ATP and GTP) on phosphodiesterase (PDE) of brain and outer segments of the retina enriched or devoid of protein modulators were studied. In the case of retinal outer segment PDE the enzyme activity was considerably inhibited by both nucleosides only when the enzyme was separated from the inhibitor. In case of brain PDE, on the contrary, the effect of the nucleosides was much more pronounced in the enzyme preparation coupled with the protein activator, calmodulin. The latter when added to brain PDE devoid of the activator in the presence of ATP and GTP considerably reduced the enzyme activity. An addition of the inhibitor simultaneously with GTP to the purified PDE of outer segments increased the PDE activity. The constants for the inhibition of brain PDE coupled with calmodulin and retinal outer segment PDE separated from the inhibitor by ATP and GTP were determined.     

Kinetic and proteolytic identification of heat-induced conformational changes in the urea herbicide binding site of isolated Phaseolus vulgaris chloroplast thylakoids

Kinetic parameters of 3-(3, 4-dichlorophenyl)-1, 1-dimethyl urea (DCMU)-induced inhibition of electron transport in chloroplast thylakoids isolated from Phaseolus vulgaris L. cv. Oregon 1604 were determined from analysis of a convergent, parallel electrical circuit. Through this analogue, the apparent affinity of the purported binding site for DCMU (K₁) and the relative amount of DCMU-insensitive electron transport (v^max₁/v_o) were obtained using a reiterative non-linear least squares curve-fitting procedure. Exposure of thylakoids to heat caused a gradual increase in K₁ (or decrease in the affinity of the thylakoid for DCMU) with an apparent activation energy of 134 kJ mol⁻¹. Tryptic susceptibility of a protein region regulating K₁ also decreased gradually with exposure to 45°C, suggesting that the heat-induced increase in K₁ might be due to a protein conformational change. On the other hand, thylakoid exposure to 45°C resulted in a rapid (<5 min) irreversible increase in v^max_I/v_o, which was also the apparent result of a conformational change in a region of the protein which regulates this function. These results are suggestive of the existence of differential thermal sensitivities of proteins within the thylakoids and, perhaps, of different regions within a single membrane protein.     

Susceptibility of human and murine Chlamydia trachomatis serovars to granulocyte- and epithelium-derived antimicrobial peptides.

Four antimicrobial peptides, protegrin-1, RTD-1, cryptdin-4, and indolicidin, were tested for their ability to inhibit the in vitro growth of Chlamydia trachomatis serovars E, L2, and mouse pneumonitis (MoPn). In general, protegrin-1 was found to have the strongest anti-chlamydial activity. Overall, of the three serovars tested, L2 was the most susceptible while MoPn was the most resistant to these peptides.