Biomedical subjects
Publications and source records attributed to R L Adams.
Although echinomycin is reported to intercalate and to bind to DNA at CG dinucleotides, the effects of the drug on DNA methylation in vitro and in vivo are much less apparent than are the effects on DNA synthesis and cell growth.
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We have purified the DNA methylase from mouse ascites tumour cells to a specific activity of 11,500 units per mg protein using denatured Micrococcus luteus DNA as methyl acceptor. Methyl groups are transferred to cytosines almost exclusively in CpG dinucleotides. The purified enzyme contains two polypeptides of molecular mass 185 and 160 kDa, and an antiserum raised in a rabbit to the purified enzyme specifically reacts with these two proteins in crude extracts. The two proteins can be partially separated by affinity chromatography when activity is associated with the 185 kDa protein which can be proteolytically degraded to give polypeptides of 170 and later 100 and 50 kDa. Only the 185 kDa methylase is lost when cells are treated with azadeoxycytidine and this is the predominant form firmly bound in the nucleus of dividing cells. Antibody bound to the 185 kDa band in protein blots will itself bind native DNA methylase, which can be detected by its binding 14C-labelled, azacytosine-containing DNA.
The endogenous DNA methylase in nuclei isolated from growing mouse cells preferentially methylates DNA in micrococcal nuclease-resistant regions probably as a result of the location in these regions of the preponderance of hemimethylated sites. Added mouse ascites cell DNA methylase catalyses the methylation of exposed, nuclease-sensitive DNA in chromatin from growing or non-growing mouse or insect cells. The poor acceptor ability of nuclease-resistant regions in this situation is due to the presence of histone proteins which block de novo methylation. Transcriptionally active regions of chromatin are selectively methylated in vitro by either endogenous or added DNA methylase.
Turkey males subjected to a low intensity step-down (LISD) lighting programme showed significantly heavier body weights after 20 weeks of age and significantly better feed conversions after 14 weeks of age compared with males reared in a high intensity step-up lighting (HISU) programme. Although both nonchilled and chilled carcase weights were higher, the dressing percentages were lower for males of the LISD lighting regimen. Males of the HISU lighting programme had significantly fewer leg abnormalities, shorter tarso-metatarsi, lighter drumstick weights, and lighter tibia weights. Males on the HISU lighting programme from 15 to 19 weeks of age had larger testes; however, after 20 weeks of age they were larger in males on the LISD lighting regimen. Cleaning and disinfecting the drinking troughs daily rather than weekly had no effect on any production variable measured.
Effects of age on the growth, feed to gain ratios, individual part weights, and yields of hen turkeys were determined weekly from ages 12 to 21 weeks. Two hundred birds from each of three strains (A, B, and C) were processed. All three strains of hen turkeys continued to gain weight throughout the study. During the 12 to 21-week-old period birds grew from an average of 4.76 kg to 9.17 kg, while the cumulative feed to gain ratios went from 1.97 to 2.94. Strain B consistently weighed more than Strains A and C for the duration of the study. Weights of all parts increased as hens grew larger. However, the parts' proportion of total weight changed. Percentages of breast, breast muscle, and fat increase, while percentages of wing, drumstick, and skin decreased. Breast, breast muscle, and fat yields increased from 32.8 to 35.9%, 23.8 to 28.0%, and 1.7 to 5.1%, respectively. Both wing and drumstick percentages declined from approximately 14.0 to 12.0%. Thigh, thigh muscle, and shell percentages varied, but ended near their starting levels, of 14.8, 10.5, and 21.8%, respectively. At 21 weeks of age the hen turkeys were still gaining body weight. Breast weight--both actual and percentages--were still increasing.
In this article, the neuropsychology of dementia is discussed with special attention given to Alzheimer's disease. The clinical use of neuropsychological testing in neurologic practice is presented along with relevant recent research in the area.
Previous procedures for the extraction of DNA methylase (EC 2.1.1.37) from nuclei of mouse ascites cells have involved the use of buffers containing 0.2M NaCl. Whilst such 'soluble' methylase accounts for the bulk (70-80%) of DNA methylase activity a further portion of activity is detectable in a 'bound' form firmly associated with 2 M NaCl-resistant nuclear matrix-like structures. This association, which in part requires continuing DNA replication and protein synthesis, can, however, be disrupted in vitro with high concentrations of ammonium sulphate, and the enzymic properties of the 'bound' form of DNA methylase are similar to those described for the 'soluble' form.
It is shown that the methylation of DNA that occurs in isolated nuclei is "delayed methylation". This methylation is not reduced in nuclei which have been pretreated with 0.2M NaCl to extract the soluble methylase suggesting that this methylation is the product of a firmly bound matrix associated DNA methylase. Evidence is provided that, like the methylase, the DNA substrate is associated with the nuclear matrix.
In a preliminary study, hydrocortisone-treated rats developed pseudotuberculosis when challenged with 6.2 X 10(5) to 3.1 X 10(7) colony forming units of Corynebacterium kutscheri by intranasal, intragastric, or subcutaneous inoculation. Oronasal exposure was selected as a likely natural route to further study inapparent infection. In Study 1, 50 rats received 1.2 X 10(5) colony forming units and various tissues were cultured at intervals to 12 weeks post-inoculation. At each interval, C. kutscheri was regularly isolated from submaxillary lymph nodes, but isolation was sporadic from other sites. In Study 2, 17 out of 21 rats given 1.2 X 10(5) colony forming units and killed weekly for 6 weeks had 2.0 X 10(2) to 1.8 X 10(5) colony forming units of C. kutscheri in oral washes, and 16 rats had 2.0 X 10(2) to 1.0 X 10(5) colony forming units in submaxillary lymph nodes, Serum antibody to C. kutscheri using both microagglutination and indirect immunofluorescence was first detected in some rats by 2 weeks, and in all rats at subsequent intervals. There was a significant (P less than 0.001) positive correlation (r = 0.93) between serum antibody titers and the duration of infection.
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The vertebrate genome is a mosaic of regions differing dramatically in their G + C content. Those regions with a high G + C content contain the expected number of CpG dinucleotides and we propose that following methylation these have been protected from deamination by the increased stability of the surrounding DNA duplex. This argument applies both to the microenvironment of the CpG dinucleotide and to whole gene regions.
We have previously described an idiotype (Id460) that transiently dominates anti-2,4-dinitrophenyl (DNP) antibody responses of mice that possess the appropriate Igh-V and V kappa genotypes. Normal serum has significant levels of Id460 that does not bind DNP, and hybridomas derived from spleen cell fusions that produce monoclonal antibodies with these characteristics have been generated. Many of these monoclonal, Id460-positive antibodies bind the opportunistic mouse pathogen Pasteurella pneumotropica. P. pneumotropica induces a marked increase in serum Id460 titers without significantly increasing serum anti-DNP titers. Both normal serum and P. pneumotropica-induced Ig460-positive immunoglobulin specifically bind to P. pneumotropica. These results suggest that the normal serum Id460-positive immunoglobulin is induced by environmentally encountered antigens on P. pneumotropica. We propose that this naturally occurring Id460 activates antiidiotypic regulatory cells that in turn promote production of Id460-positive anti-DNP antibody following DNP-ovalbumin immunization. These data are compatible with those obtained in several other idiotypic systems that suggest that dominant idiotypes may be associated with antibodies that have been evolutionarily selected for expression because of their specificity for antigens on environmentally encountered pathogens.
Herpes simplex virus type 2 is demonstrated in routine cervical smears by immunocytochemistry. Optimum antibody dilution and suitable fixation were determined and immunostaining results were found to compare favourably with those obtained by screening Papanicolaou-stained smears or by virus culture methods (virus isolation). Results obtained for immunostaining of smears from 158 patients agreed with those of virus isolation in 47 of 50 cases where virus isolation was performed. It is suggested that this immunocytochemical technique is valuable in detection of Herpes simplex virus in cervical smears, offering an inexpensive and rapid laboratory diagnosis with advantage to both patient and clinician.
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We report an unusual case of anorectal syphilis. The literature reviewed supports the difficulty in identifying the varied presentations of this disease. Diagnostic and therapeutic maneuvers are based on an understanding of the pathophysiology of luetic infections. Penicillin remains the drug of choice in treating all stages of syphilis.