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Biomedical subjects

J Allan

Publications and source records attributed to J Allan.

At least 91 records · Page 5Linked to original sources
PubMed1984

Accumulation of the isolated carboxy-terminal domain of histone H1 in the Xenopus oocyte nucleus.

Histone H1 accumulates in the nucleus after injection into the cytoplasm of Xenopus oocytes. A proteolytic fragment of 89 amino acids encompassing the carboxy-terminal domain also accumulates in the nucleus. Lysine, alanine and proline compose 84% of this domain. Accumulation is not due solely to the high lysine content since poly-L-lysine does not accumulate in the nucleus when injected into the cytoplasm of Xenopus oocytes. Proteolytic fragments encompassing other domains of the molecule are degraded in the oocyte after injection. In these instances degradation is more rapid in the cytoplasm than in the nucleus giving the false impression of accumulation in the nucleus, an artefact which is likely to confuse other studies of protein migration. Susceptibility to rapid degradation is a dominant feature, thus the globular domain destabilises the contiguous carboxy-terminal domain. The properties of the carboxy-terminal domain of H1 and the possible involvement of the amino acids lysine, proline and alanine in migration are discussed and compared with those of a domain that specifies migration of nucleoplasmin into the oocyte nucleus.

Animals↗
PubMed1984

Higher order structure in a short repeat length chromatin.

Polynucleosomes from calf brain cortical neurone nuclei have an average repeat length of less than 168 base pairs. The ability of this material to adopt higher order structure has been assessed by various physical techniques. Although containing on average less DNA per nucleosome than is required to form a chromatosome, this short repeat length chromatin folded in an H1 dependent manner to a structure with properties similar to those observed for longer repeat length chromatins such as that of chicken erythrocyte (McGhee, J.D., D.C. Rau, E. Charney, and G. Felsenfeld, 1980, Cell, 22:87-96). These observations are discussed in the context of H1 location in the higher order chromatin fiber.

Animals↗
PubMed1984

HTLV and immunosuppression.

There is increasing evidence for the link between members of the human T-lymphotropic virus family and clinically important disease. We used indirect membrane immunofluorescence (IMI) to screen patient and control sera for antibodies to human T-cell leukemia virus (HTLV) specific cell membrane antigens (HTLV-MA) of HTLV-I and HTLV-III. Representative sera were screened for antibodies to specific HTLV-encoded proteins using radioimmunoprecipitation (RIP) with SDS-polyacrylamide gel electrophoresis (SDS-PAGE). Essentially all Japanese patients with adult T-cell leukemia/lymphoma (ATLL) from Miyazaki, Japan had detectable antibodies to HTLV-I-MA, further supporting the evidence for the probable etiologic relationship of HTLV-I and ATLL. While 16% of the healthy adults from this endemic region had antibodies to HTLV-I-MA, such antibodies were also found in 42% of the adults hospitalized in Miyazaki with severe infections diseases. Other studies have demonstrated HTLV-I antibodies in 12% of asymptomatic hemophiliacs examined from various U.S. cities. We have previously shown that HTLV-I status positive antibody in hemophiliacs is accompanied by a decrease in the number of T helper cells. Patients seropositive for antibodies to HTLV-I-MA regularly demonstrated antibodies to the env gene encoded gp61 proteins, while lower but significant proportions had antibodies to the gag and lor gene proteins. These and other observations suggest that infection with at least some strains of HTLV-I may be associated with mild or transient immunosuppression, in the absence of leukemia. Analysis by RIP indicated that gp61 and gp45, both encoded by the env gene of HTLV-I, are the most immunogenic proteins of the virus. The gp61 HTLV-I is highly crossreactive with gp67, the major env protein of HTLV-II. Patients with acquired immune deficiency syndrome (AIDS) were also examined for antibodies to HTLV-I-MA and antibodies to the gag, env, and lor gene proteins by RIP. Antibodies were detected in 38-75% of the patients, the higher percentage reflecting the presence of at least one positive sample in those individuals where more than three serial serum samples were tested. Numerous control groups were essentially seronegative for antibodies to HTLV-I proteins. When AIDS patient sera were examined for antibodies to HTLV-III, 95-100% were seropositive. Such antibodies were also found in the majority of asymptomatic Boston-areas hemophiliacs.(ABSTRACT TRUNCATED AT 400 WORDS)

Acquired Immunodeficiency Syndrome↗
PubMed1983

Acute respiratory infection in childhood: the factors which influence hospital admission.

A study of 100 children admitted to hospital with acute respiratory infection revealed that general practitioners remain the major referral source. Changing financial factors do not appear to have influenced this process. Sixty percent of children had a mild illness, requiring a short period hospital stay, but their referral was on a medical rather than a social basis.

Acute Disease↗
PubMed1983

Modulation of the relative trypsin sensitivities of the core histone 'tails'.

The order in which the core histone tails in chicken erythrocyte chromatin are attacked by trypsin has been reinvestigated. Results are presented to demonstrate that in the absence of linker histones H1 and H5 the relative order of core histone degradation by trypsin can be altered by changing the salt environment. In native chromatin, the presence of linker histones H1 and H5 inhibits this salt-dependent transition.

Animals↗
PubMed1983

Asthma, air pollution and climate: a Christchurch study.

The relationship of hospital attendances for acute asthma attacks to air pollution levels in Christchurch was studied over the winter months of 1981. Attendances for acute asthma did not increase with increases in air pollution; indeed, higher pollution tended to be characterised by lower hospital attendances. This trend increased when multiple regression analysis was used to control the effects of climatic factors.

Adult↗
PubMed1983

Inhaled Fenoterol powder in asthma: a long term study.

A study was designed to assess the long term efficacy of Fenoterol powder in asthmatic children. The design included an initial assessment period and a further evaluation after six months, in which Fenoterol or placebo treatments were administered on consecutive days. Objective measurements were obtained from PEFR and FEV1. A diary record was kept to monitor compliance and side effects. A minimum dose of 200 mcg Fenoterol powder was prescribed three times per day. The bronchodilator action of Fenoterol was sustained after a period of six months, in the absence of significant side effects.

Adolescent↗
PubMed1983

Mutations at more than one locus may be involved in cystic fibrosis--evidence based on first-cousin data and direct counting of cases.

Cystic fibrosis was present in 35 of 5,265 first cousins of index cases with the disease. The gene frequency was estimated to be .0281 +/- .00544, using an improved method that allows for the influence of cousin sibship size upon the estimate. This figure is higher than that obtained by direct counting of cases in Victoria, Australia, from 1955-1979 (.0198 +/- .000127), raising the possibility that multiple gene loci may be involved in this disease. Further analysis showed that the number of affected first cousins fitted very well with an expected number based on a model involving two gene loci, each responsible for half the cases of cystic fibrosis. Agreement with expectations based on a single locus was not good. An alternate explanation of gross underascertainment of cases is dismissed because the index sibships were shown to fit very closely a truncate binomial distribution. The gene frequencies at the putative two loci would then each be .0140 and heterozygote frequencies one in 36. One in 18 people would be heterozygous at either one or the other of the loci.

Adult↗
PubMed1982

Antibodies against the folding domain of histone H5 cross-react with H1(0) but not with H1.

Antibodies to the folding domain (residues 22-100) of histone H5 were elicited in rabbits. Analysis of the specificity of these antibodies by enzyme-linked immunoassay and by diazobenzyloxymethyl cellulose transfer techniques revealed that the antibody cross-reacts strongly with intact H5 and histones H1(0)a and H1(0)b purified from ox liver but not with the four core calf thymus, or with high mobility group proteins. We conclude that the globular region of H5 is serologically homologous to that of H1 degrees and suggest that possible functional similarities between the two proteins reside in this region.

Animals↗
PubMed1982

Participation of core histone "tails" in the stabilization of the chromatin solenoid.

We show here that the solenoid is maintained by the combination of linker histones and the nonglobular, highly basic "tails" of the core histones, which play only a minor part in the formation of the nucleosome core (Whitlock and Simpson, 1977. J. Biol. Chem. 252:6,516--6,520; Lilley and Tatchell, 1977. Nucleic Acids Res. 4:2,039--2,055; and Whitlock and Stein, 1978. J. Biol. Chem. 253:3,857--3,861). Polynucleosomes that contain core histones devoid of tails remain substantially unfolded under conditions otherwise favorable for the formation of solenoids. The tails can be replaced by extraneous basic polypeptides and in the presence of the linker histones the solenoid structure is then spontaneously recovered, as judged by a wide variety of structural criteria. The inference is that the core histone tail segments function by providing electrostatic shielding of the DNA charge and at the same time bridging adjacent nucleosomes in the solenoid. Our results carry the further implication that posttranscriptional modifications, such as acetylation of epsilon-amino groups, that reduce the positive charge of the core histone tails will tend to destabilize the higher-order structure and could thus render the DNA with which they are associated more readily available for transcription.

Centrifugation, Density Gradient↗
PubMed1981

Regulation of the higher-order structure of chromatin by histones H1 and H5.

Chicken erythrocyte chromatins containing a single species of linker histone, H1 or H5, have been prepared, using reassembly techniques developed previously. The reconstituted complexes possess the conformation of native chicken erythrocyte chromatin, as judged by chemical and structural criteria; saturation is reached when two molecules of linker histone are bound per nucleosome, as in native erythrocyte chromatin, which the resulting material resembles in its appearance in the electron microscope and quantitatively in its linear condensation factor relative to free DNA. The periodicity of micrococcal nuclease-sensitive sites in the linker regions associated with histone H1 or H5 is 10.4 base pairs, suggesting that the spatial organization of the linker region in the higher-order structure of chromatin is similar to that in isolated nucleosomes. The susceptible sites are cut at differing frequencies, as previously found for the nucleosome cores, leading to a characteristic distribution of intensities in the digests. The scission frequency of sites in the linker DNA depends additionally on the identity of the linker histone, suggesting that the higher-order structure is subject to secondary modulation by the associated histones.

Animals↗
PubMed1980

The structure of histone H1 and its location in chromatin.

On the basis of their primary structure, the lysine-rich histones are a unified family of proteins. Each has an amino acid chain which falls into three distinct domains. Only the central domain (approximately 80 residues) is in a folded conformation. It is protected from trypsin digestion in chromatin and corresponds to the segment of highest sequence conservation. Without the flanking domains it is able to close two full turns of DNA in the nucleosome and can thus locate the H1 molecule.

Amino Acid Sequence↗
PubMed1980

An examination of models for chromatin transcription.

Structural studies have revealed that chromatin is composed of repeating units or nucleosomes having two distinct domains, the nucleosome core and the linker region. The nucleosome core comprises 146 base pairs of DNA wound in one and three quarter turns around an octamer of histones made up of two symmetrical tetramers (1). It may be inferred on topological grounds that this structure must be perturbed during chromatin transcription and replication since the histone core bridges the supercoil which blocks the passage of polymerase along the template and prevents the unwinding of DNA required for enzymatic copying. A number of mechanisms for freeing the DNA template may be envisaged, and one detailed model, based on symmetrical dissociation of the histone tetramers, has been proposed (2). Here we present evidence against such unpairing or indeed any detachment of histones from the octamer during chromatin transcription, and we give reasons for favouring a transcriptional mechanism based upon the separation of the octamer from at least one of the DNA.

Animals↗
PubMed1980

Reversible dissociation of linker histone from chromatin with preservation of internucleosomal repeat.

Procedures are described for the dissociation of histones H1 and H5 from chicken reticulocyte chromatin without disruption of the native core histone-DNA complex. The comparative properties of native and depleted chromatin with respect to sedimentation, thermal denaturation, and sensitivity to nuclease digestion have been studied. The changes in these properties resulting from removal of the linker histones are fully reversed when histone H5 is added back to the depleted chromatin.

Animals↗
PubMed1980

Blood group glycosyltransferase activities in plasma from blood chimera subjects.

Blood group glycosyltransferases (A and B) in plasma are mainly derived from other tissues, not from bone marrow where the blood group substances are synthesized. Therefore, it is possible to determine the original blood type of host subject and grafted cells by examining the enzyme activity in plasma from a chimera subject. Subject WD had 75-85% of O type cells and 15-25% of A1 type cells. A1 enzyme activity of the subject's plasma was the same as control A1 plasma, suggesting that subject WD is genetically A1O or A1A1 and O red cells are produced by OO bone marrow cells acquired in utero. Another subject EA has about 85% of B type and 15% of A1B type red cells. B enzyme activity of the subject's plasma is normal, but A enzyme activity is only 20% of normal level. Subject EA must be genetically BO or BB, and A gene is restricted to bone marrow cells acquired.

ABO Blood-Group System↗