Nucleosomes arrangement in chromatin

The spatial arrangement of nucleosomes in rat liver chromatin has been examined using the electric birefringence technique. All chromatin subunits studied (up to 9 consecutive nucleosomes) contain their full complement of the five histone types associated with about 200 base pairs repeat length DNA.     

A physical map of belomycin-specific fragmentation sites on PM2 bacteriophage DNA

Bleomycin treatment of PM2 DNA results in fragmentation of the genome at several specific sites. Application of restriction endonuclease digestion followed by bleomycin treatment has provided the basis for constructing a physical map of bleomycin fragmentation sites. Eleven sites have been located on the physical map relative toHpa II,Pst I, andHindIII cleavage sites. The fragmentation sites are not clustered in a particular region of the PM2 genome but 3 of the 11 sites do occur between theHpa II andPst I cleavage sites, a segment of DNA which comprises 14% of the PM2 DNA length.     

The taxonomic and ecological status of the environmentally restricted Spongillid species of North America. II. Anheteromeyenia biceps (Lindenschmidt, 1950)

The taxonomic validity, present distribution, and specific threats to the existence of the freshwater sponge, Anheteromeyenia biceps (Lindenschmidt, 1950) were investigated. The species, reported only from the type locality, Bessey Creek and Maple River, two streams flowing into Douglas Lake, Michigan, is relegated to synonomy with Ephydatia mülleri. Habitat data from Bessey Creek and Maple River, particularly physicochemical data, greatly extend the known environmental parameters of Heteromeyenia tubisperma and Ephydatia mülleri.     

Ultrastructural studies on erythropoiesis in the avian thymus

The cortex of enlarging thymic lobes from adult haemorrhaged Quelea quelea were found to be similar to those of wild birds where the thymic enlargement was occurring naturally. A detailed stereological analysis of cells broadly designated as lymphoid, and the construction of models to account for the results, indicates that the enlarging thymic lobe contains both large and small blast cells, a heterogenous group of medium lymphocytes, erythroid cells, and two types of very small lymphocytes. The distinction between early erythroid cells and some lymphocytes, despite this detailed analysis is very difficult, but it is possible in enlarging thymic lobes that up to 42% of the lymphoid cells may have erythroid characteristics.     

Multiple molecular forms of lysosomal enzymes in mucolipidosis II

Summary The multiple molecular forms of selected lysosomal enzymes, as determined by analytical isoelectric focusing electrophoresis, from mucolipidosis II fibroblasts have a highly simplified pattern demonstrating a failure to undergo normal oligosaccharide processing. On the other hand, the multiple molecular forms of these same enzymes in mucolipidosis II sera and culture media are indistinguishable from controls.     

Two specific ribonucleoprotein fragments from rat liver 60S ribosomal subunits

K+-depleted 60S ribosomal subunits from rat liver were submitted to a mild treatment with ribonuclease T1. Ribonucleoprotein fragments could be separated on sucrose gradients only when the digested subunits were partially deproteinized with a high KCl concentration (0.6 M) which removed seven proteins more or less completely and 5S RNA. The RNA and protein content of each fragment has been characterized. The largest ribonucleoprotein enclosed two RNA fragments of about 950,000 and 750,000 daltons and all the salt-resistant proteins except L5. The smallest one enclosed protein L5 (with L11, L17 and L26 in small amounts) and a 67,000 RNA piece. The subsequent hydrolysis of the large ribonucleoprotein produced several other ribonucleoproteins. One of them has been fully characterized: it enclosed a 250,000 RNA fragment and protein L12 (with L11, L25 and L30 in smaller amounts).     

Effect of ribonuclease T1 on ribosomal subunits of rat liver.

The accessibility of 28S RNA within the ribosomal subunits to ribonuclease T1 was studied, in comparing results obtained after enzyme treatment of compact, K+ deficient 60S subunits and of EDTA-treated 60S subunits. RNA, extracted from the subunits, using a mixture of sodium dodecyl sulfate and phenol was analyzed on sucrose gradients. The RNA from active subunits was only degraded in high enzyme concentrations. In the K+ deficient subunits, RNA is more accessible since it breaks down into 6 well-defined fragments, sedimenting between 4S and 18.5S. Within the EDTA-subunits, there is no more protection of the RNA. In fact, it is degraded by weak enzyme concentrations, as is the free 28S RNA, giving heterogeneous fragments. Comparison of the melting curves of subunits and free 28S RNA showed that it is only in EDTA subunits that proteins do not stabilize the secondary structure of RNA. In the case of 40S subunits, the action of ribonuclease T1 combines with the action of the endogenous nuclease which makes the degradation process more difficult to analyze.     

Detection of ischemia-reperfusion cardiac injury by cardiac muscle chemiluminescence

Various methods have been used in the past to assess the implication of oxygen free radicals (OFR) in ischemia-reperfusion-induced cardiac injury. Luminol-enhanced tert-butyl-initiated chemiluminescence in cardiac tissue reflects oxidative stress and is a very sensitive method. It was used to elucidate the role of OFR in cardiac injury due to ischemia and reperfusion. Studies were conducted on perfused isolated rabbit hearts in three groups (n = 8 in each): I, control; II, submitted to global ischemia for 30 min; III, submitted to ischemia for 30 min followed by reperfusion for 60 min. The heart tissue was then assayed for chemiluminescence (CL); content of malondialdehyde (MDA), an indicator of OFR-induced cardiac injury; and activity of tissue levels of antioxidants [superoxide dismutase (SOD), catalase, glutathione peroxidase (GSH-Px)].The control values for left and right ventricular CL and malondialdehyde were 81.1 ± 15.4 (S.E.) and 182.4 ± 50.3 (S.E.), mv-min-mg protein^–1; and 0.024 ± 0.006 (S.E.) and 0.324 ± 0.005 (S.E.) nmoles-mg protein^–1 respectively. Ischemia produced an increase in the cardiac CL (3.3 to 4.4 fold) and MDA content (2 to 2.6 fold). Reperfusion following ischemia also produced similar changes in CL and MDA content. The control values for activity of left ventricular SOD, catalase, and GSH-Px were 45.77 ± 1.73 (S.E.) U-mg protein^–1 5.35 ± 0.51 (S.E.) K-10^–3-sec^–1-mg protein^–1, and 77.50 ± 7.70 (S.E.) nmoles NADPH-min^–1-mg protein^–1 respectively. Activities of SOD and catalase decreased during ischemia but were similar to control values in ischemic-reperfused hearts. The GSH-Px activity of left ventricle was unaffected by ischemia, and ischemia-reperfusion. GSH-Px activity of the right ventricle increased with ischemia, and ischemic-reperfusion.These results indicate that cardiac tissue chemiluminescence would be a useful and sensitive tool for the detection of oxygen free radical-induced cardiac injury.     

Detection of human papillomavirus types by the polymerase chain reaction and the differentiation between high-risk and low-risk cervical lesions

By means of a consensus polymerase chain reaction (PCR) method, the prevalence of HPV types was determined in cervical biopsies from 137 women referred to the gynecological outpatient clinic for colposcopy because of an abnormal cervical smear. The prevalence of HPV was 80.3%. There was a statistically highly significant rise in the prevalence of the oncogenic HPV types (16, 18, 31, 33) with increasing severity of cervical intraepithelial neoplasia (CIN I to III), indicating a role for these HPV types in the pathogenesis of cervical cancer. The prevalence of other HPV types decreased significantly with the severity of the lesion, suggesting that these HPV types play a less significant role in this process. These data indicate that HPV typing with PCR may be a valuable tool for distinguishing between highrisk and low-risk cervical lesions. Furthermore, our results suggest that the detection of HPV types by consensus PCR in the cervix of patients with an abnormal smear but without histologically detectable CIN is a useful tool for predicting which of these patiens will eventually develop CIN. Finally, a relatively low percentage (3%) of HPV double infections is reported in this study.