Electrophoretic behavior of the H+-ATPase proteolipid from bovine heart mitochondria

The proteolipid subunit of H⁺-ATPase was labeled by [¹⁴C]N,N-dicyclohexylcarbodiimide in bovine heart mitochondria. The radioactive labeling was followed using various systems of sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE). When using discontinuous SDS-PAGE (Laemmli, U.K., 1970,Nature (London)227, 680–685) a monomeric (Mr 7600±1500) and a dimeric form (Mr 17,800±1200) of the proteolipid were detected, while only the monomeric form was found on urea (8 M) containing gels (SDS-PAGE according to Laemmli; or Swank, R. T., and Munkers, K. D., 1971,Anal. Biochem. 39, 462–477). When using SDS-PAGE with Na-P_i buffer (Weber, K., and Osborn, M., 1969,J. Biol. Chem. 244, 4406–4442), only a dimeric form of the proteolipid (Mr 15,000±1000) was detected. Experimental data indicate that the different patterns of proteolipid separation are related to the presence of the two distinct proteolipid conformations in the SDS solution.     

The superstructure of chromatin and its condensation mechanism

Synchroton radiation X-ray scattering experiments have been performed on chicken erythrocyte chromatin fibres over a wide range of ionic conditions and on various states of the fibres (i.e. "native" in solution, in gels and in whole nuclei; chromatin depleted of the H1 (H5) histones and chromatin with bound ethidium bromide). A correlation between the results obtained with the various chromatin preparations provides evidence for a model according to which at low ionic strength the chromatin fibre already possesses a helical superstructure, with a diameter comparable to that of condensed chromatin, held together by the H1(H5) histone. The most significant structural modification undergone upon an increase of the ionic strength is a reduction of the helix pitch, this leads to condensation in a manner similar to the folding of an accordion. The details of this process depend on whether monovalent or divalent cations are used to raise the ionic strength, the latter producing a much higher degree of condensation. Measurements of the relative increase of the mass per unit length indicate that the most condensed state is a helical structure with a pitch around 3.0-4.0 nm. In this paper we give a detailed presentation of the experimental evidence obtained from static and time-resolved scattering experiments, which led to this model.     

Nucleotide sequence of the rice cytochrome f gene and the presence of sequence variation near this gene

The rice (Oryza sativa L. var. Labelle) chloroplast (cp) gene encoding cytochrome f has been isolated and sequenced. The coding region of this rice gene displays 95.1%, 85.3% and 85.2% nucleotide sequence homology with that of wheat, pea and spinach, respectively. To examine the cpDNA sequence variation in rice, cpDNA from Labelle and its parents, Belle Patna and Dawn was compared. Using the cytochrome f gene as the probe for hybridization, we found several differences in the size and number of restriction fragments in the cp genome of three rice varieties. An additional restriction fragment found in the Belle Patna cp suggests that this cp genome is either heterogeneous or contains two copies of cytochrome f gene per cpDNA.     

On the dynamics of the mass mortality of Diadema antillarum in Barbados

Widespread mortality of the black sea urchin Diadema antillarum occurred in the Caribbean in 1983; beginning in Panama in January, and having its major impact at Barbados in September. Mortality on ten reefs surveyed in Barbados was 93.2%, with the highest being 99.9% and the lowest 86.9%. Mortality on each reef was independent of the pre-mortality density on the reef. Urchins with test diameters between 20 and 40 mm were more severely affected than smaller or larger urchins. Populations on reefs exposed to incoming oceanic water suffered heavier mortality than those on protected reefs. Mean size of urchins was smallest on high density reefs. This may indicate a negative effect of density on urchin growth. At post-mortality densities, urchins may grow faster and reach sexual maturity sooner.     

Biphasic mode of epithelial regeneration in murine pulmonary alveoli

After administration to mice of butylated hydroxytoluene, the pulmonary alveolar epithelium adopts a biphasic pattern of regenerative proliferation. This hitherto-unnoticed pattern of epithelial repair in the lung was revealed by the investigation of stereologic parameters. The earliest evidence of epithelial injury involved the type I pneumocytes, whose necrosis and disappearance from the septal surface was shown by a lowered surface density (SV). Proliferation of the type II pneumocytes ensued: the volume density (VV) rose above normal soon after the onset of necrosis, only to decrease as the cells slowly differentiated into intermediate and then type I pneumocytes. A second peak of type II pneumocytes appeared as the denuding of septa persisted. This twofold proliferation was also shown by the numerical density count (NV). Differentiation into an intermediate pneumocyte was itself documented by the raised VV and SV values. These observations of a biphasic mode of proliferation of type II pneumocytes raise the question of an unsuspected, persistent action of the toxic agent within pulmonary alveoli and serve to document the homeostasis of epithelial regeneration.     

Randomised trial of compliance with screening for colorectal cancer.

A randomised trial of compliance with screening for colorectal cancer by means of the haemoccult test was conducted in Farnborough and Basingstoke districts. In each of the 14 participating practices (41 general practitioners) 25 852 men and women aged between 40 and 70 years were randomly allocated by household to one of six groups. The group determined the method of invitation to screening: a letter and the test were sent to the patient, or a letter with an appointment to attend the surgery was sent, or during a routine consultation the general practitioner invited patients to participate, and some patients received an educational booklet about bowel disorders and screening. Of the 17 824 people who were offered screening, 7545 (42%) complied. Compliance was significantly affected by the method of invitation, but not by whether an educational booklet was received, and was highest (57%) in the group that was offered the haemoccult test during a routine consultation (the "opportunistic" approach). In this group the compliance rate achieved by individual general practitioners ranged from 26% to 82%. Compliance was significantly higher in Farnborough, in the older (55-70) age group, in women, and in households in which two or more people were offered screening. The higher compliance in Farnborough may be explained by the higher proportion of older people and by the higher proportion of people living in households of two or more in the population that was offered screening. The fact that the screening programme in Farnborough was offered to the whole community and that the researcher may have acted as a facilitator were probably also important. One per cent of the patients screened had a positive test, and 24 (38%) of the 63 patients who were positive and were investigated in hospital had neoplastic disease. The yield was 1.2 cancers and 1.2 benign adenomas (1 cm or larger in size) per 1000 people screened. This low yield is likely to be a consequence of the relatively young age group screened.