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H R Matthews

Publications and source records attributed to H R Matthews.

At least 127 records · Page 7Linked to original sources
PubMed1984

Patterns of histone acetylation in Physarum polycephalum. H2A and H2B acetylation is functionally distinct from H3 and H4 acetylation.

Histone acetylation has previously been correlated with both chromosome replication and transcription. We present evidence that (a) confirms both correlations in the true slime mold, Physarum polycephalum and (b) shows that quite a different pattern of acetate turnover is associated with replication compared with transcription. The pattern associated with replication involves turnover of acetate on all four core histones on species containing one or two acetates per molecule. This pattern was resolved from the transcription-associated pattern by three different procedures: (a) detailed analysis of gels of histones pulse-labelled with acetate; (b) the pattern of acetylation of histones pulse-labelled with [3H]lysine; and (c) the pattern of acetylation of soluble histones. The pattern associated with transcription is restricted to histones H3 and H4 and occurs mostly on highly acetylated species. This pattern was resolved by (a) analysis of gels of histones pulse-labelled with acetate; (b) the pattern of histone acetylation in G2 phase of the cell cycle; and (c) the pattern of histone acetylation in the presence of cycloheximide.

Acetates↗
PubMed1984

5-Methyldeoxycytidine in the Physarum minichromosome containing the ribosomal RNA genes.

5-Methyldeoxycytidine (5MC) was analyzed by high pressure liquid chromatography (HPLC) and by restriction enzyme digestion in rDNA isolated from Physarum polycephalum. rDNA from Physarum M3C strain microplasmodia has a significant 5MC content (about half that of the whole genomic DNA). This rDNA contains many C5MCGG sites because it is clearly digested further by Msp I than by Hpa II. However, most 5MC is in other sites. In particular, alternating CG sequences appear to be highly methylated. HPLC of deoxyribonucleosides shows tha most of the transcribed regions contain little or no 5MC. Restriction digestion indicates that there is little or no 5MC in any of the transcribed regions including the transcription origin and adjacent sequences. Over 90% of the total 5MC is in or near the central nontranscribed spacer and most methylated restriction sites are in inverted repeats of this spacer. rDNA is very heterogeneous with respect to 5MC. The 5MC pattern doesn't appear to change with inactivation of the rRNA genes during reversible differentiation from microplasmodia (growing) to microsclerotia (dormant), showing that inactivation is due to changes in other chromatin variables. The 5MC pattern is different between Physarum strains. The possible involvement of this 5MC in rDNA chromatin structure and in cruciform and Z-DNA formation is discussed.

Base Sequence↗
PubMed1984

Treatment of sputum retention by minitracheotomy.

Retention of sputum is a major cause of morbidity and mortality following thoracic surgery and regular access to the trachea for suction can only be obtained either by tracheostomy or endotracheal intubation, both of which have significant disadvantages. A simple method of percutaneous tracheal cannulation for suction has therefore been developed in which a 4 mm Portex paediatric endotracheal tube is inserted through a 1 cm incision in the cricothyroid membrane, using a guarded knife and an introducer. The procedure can be performed in the ward or theatre, using local or general anaesthesia. Twenty-four patients have been treated between October 1981 and June 1982. Ages ranged from 19-80 years and the duration of cannulation from 1-45 days. No patient subsequently required any further treatment for sputum retention. Twenty-one patients made an uneventful recovery and 3 died from unrelated causes. Following decannulation healing occurred within 6 days and there were no late sequelae. The method is much simpler and less invasive than existing alternatives and can therefore be used at an early stage and before the consequences of sputum retention become irreversible.

Adult↗
PubMed1984

Nuclear protein kinases.

Nuclear protein kinases include enzymes that transfer the gamma-phosphate of ATP to serine, threonine, lysine or histidine in proteins. Nuclear kinases with a preference for basic proteins are known as histone kinases; those preferring acidic protein substrates are casein kinases. Histone kinases include both cyclic AMP-independent protein kinases and cyclic AMP-dependent protein kinases. The best-characterized cyclic AMP-independent nuclear protein kinase is associated with cell proliferation and is activated (or transported to the nucleus) in G2 phase of the cell cycle. It phosphorylates specific serine and threonine residues in the non globular domains of histone H1 and appears to promote chromosome condensation. The cyclic AMP-dependent protein kinase has unknown nuclear function(s), although it may be translocated from cytoplasm to nucleus in response to specific hormonal stimuli which are also associated with changes in transcriptional activity. There is a massive peak of nuclear cyclic AMP-dependent protein kinase activity in G2 phase of the cell cycle. Nuclear casein kinases are apparently very heterogeneous. Two of these enzymes have been purified to homogeneity. They phosphorylate non-histone chromosomal proteins, including RNA polymerase and ornithine decarboxylase. Phosphorylated ornithine decarboxylase is inactive enzymatically but, in Physarum, it binds to the rDNA minichromosome and stimulates rRNA transcription. Kinases forming phosphoramidate bonds occur in a variety of rat tissues and form phosphohistide in histone H4 and phospholysine in histone H1.

Casein Kinases↗
PubMed1984

Long latency reflex force of human finger muscles in response to imposed sinusoidal movements.

Reflex stiffness of the flexing human index finger was studied using sinusoidal movements at 3-16 Hz. The Nyquist stiffness diagram indicates the presence of a 'presonance' at around 4 Hz, its 'C' shape after correction for the mechanical properties of the relaxed finger is consistent with the involvement of a stretch reflex in its generation. This contention was supported by the presence of negative friction around 4 Hz and the disappearance of the modulation of the stiffness curve after afferent ischaemic block. Correction for the mechanical properties of active muscle, measured after afferent block, permitted the isolation of the reflex component of stiffness. The circular form of the Nyquist diagram indicates a relatively flat frequency response for the reflex over the range tested, and its radius gives a measure of reflex gain. The low value of the frequency at which the frictional force is minimal, suggests the involvement of a reflex of longer than spinal latency. This is discussed in relation to mechanisms of tremor genesis and the interaction of spinal and long latency reflexes in distal hand muscles.

Biomechanical Phenomena↗
PubMed1984

Oesophageal obstruction due to saccular aneurysm of the distal thoracic aorta.

The second reported case and first successful treatment of oesophageal obstruction due to a saccular aneurysm of the distal thoracic aorta is described. The patient, a 69-year-old male, presented with severe dysphagia which was thought to be due either to achalasia or a tumour. Operation, however, revealed a large aneurysm at the level of the diaphragmatic hiatus which was compressing the oesophagus against the right crus. As the anatomy of the aneurysm was unknown and there was a significant risk of damage to the spinal arteries the oesophageal obstruction was treated by transposition of the oesophagus combined with an anti-reflux repair. This has given an excellent clinical result and the aneurysm has remained unchanged over a period of eighteen months.

Aged↗
PubMed1984

Surgical treatment of hydrothorax complicating continuous ambulatory peritoneal dialysis.

Acute hydrothorax is a well recognized complication of continuous ambulatory peritoneal dialysis (CAPD) and is usually regarded as a contra-indication to the further use of this form of dialysis. We report the first case of treatment by surgical closure of a communication between the peritoneal and the right pleural cavity enabling CAPD to continue successfully. The development of an acute hydrothorax on CAPD is therefore not a reason to abandon this form of dialysis and can be treated by a simple thoracic surgical procedure.

Aged↗
PubMed1984

Quantitative lung scintigrams and lung function in the selection of patients for pneumonectomy.

A method for predicting postoperative respiratory function following lung resection has been used in 11 patients with both histologically proven bronchial carcinoma and chronic obstructive airways disease, in order to assess their fitness for surgical treatment. Quantitative ventilation and perfusion scintigrams were used to measure the amount of functioning tissue in each lung. These data were used in conjunction with spirometric measurements to calculate the likely functional effect of pneumonectomy. There was a high degree of correlation (r) between predicted and measured lung function for both FEV1 (r = 0.75, P less than 0.01) and FVC (r = 0.88, P less than 0.01). The postoperative FEV1 was within 150 ml of the predicted value in 45% of the patients. In the remaining patients the actual volumes were greater than predicted by 210-540 ml. For FVC the results were within 150 ml of predicted in 45% of patients and in the remainder actual volumes were greater by 160-650 ml. Both sets of calculations underestimated lung volumes by an average of 200 ml. The method is shown to be accurate, simple, non-invasive, and readily available and brings a degree of objectivity to an important decision that is often based mainly on clinical assessment.

Aged↗
PubMed1983

Acetylation and methylation sites in histone H4 from Physarum polycephalum.

Histone H4 has been isolated and purified from plasmodia of Physarum polycephalum. The four major fragments produced by hydrolysis of H4 by acetic acid were separated and the complete amino acid sequence of two of them was determined. By analogy with calf H4, these peptides are at the C-terminus and give the sequence from residue 68 to the C-terminus (residue 102). In this 35 residue sequence there are two minor differences from calf H4: (i) residue 77 is arginine in Physarum H4 and lysine in calf H4; (ii) lysine-79 is partially methylated in Physarum. Arginine occurs at position 77 in pea H4 but the occurrence of methylated lysine at position 79 has not been reported for other species. In the N-terminal region, amino acid compositions of acetic acid, tryptic and chymotryptic peptides indicate that Physarum H4 and calf H4 have identical sequences from the N-terminus to residue 47. There may be minor differences in the region from residue 46 to residue 67. The sites of acetylation were determined by Edman degradation of acetate-labelled peptide 4-17 of Physarum H4. Acetylation was observed at positions 5, 8, 12, and 16. The only other labelled peptide was the N-terminal peptide, which is not susceptible to Edman degradation and is thus probably alpha-N-acetylated as in most other organisms. The results confirm the conservation of H4 sequence and place Physarum H4 in an intermediate position between lower eukaryote H4, such as yeast or Tetrahymena H4, and higher eukaryote H4, such as mammalian H4 or pea H4.

Acetylation↗
PubMed1983

Patterns of histone acetylation in the cell cycle of Physarum polycephalum.

Labeling of histones in the naturally synchronous cell cycle of Physarum polycephalum with short pulses of tritiated acetate in vivo clearly showed three distinct patterns of histone acetate turnover. In G2 phase, turnover of acetate was observed only in histones H3 and H4, predominantly on the multiple acetylated forms. No acetate turnover was found in histones H2A and H2B compared with histones H3 and H4. In S phase, intense labeling was seen in all four core histones, in histones H3 and H4 predominantly in the low acetylated forms. In addition, cotranslational acetylation of the amino-terminal serines of histones H4 and H1 was observed during S phase. During mitosis, from condensation at prophase to decondensation after telophase, acetate turnover is almost zero. This suggests that within the mitotically condensed chromosomes all potential histone acetylation sites are masked. In G2 phase, when transcription is occurring, only histones H3 and H4 are available for acetate turnover, but in S phase, when both transcription and replication occur, all four histones are available for acetate turnover.

Acetylation↗
PubMed1983

Isolation, identification, and characterization of histones from plasmodia of the true slime mold Physarum polycephalum using extraction with guanidine hydrochloride.

Histones from plasmodia of the true slime mold Physarum polycephalum have been prepared free of slime by an approach to histone isolation that uses extraction of nuclei with 40% guanidine hydrochloride and chromatography of the extract on Bio-Rex 70. This procedure followed by chromatography or electrophoresis has been used to obtain pure fractions of histones from Physarum microplasmodia. Physarum microplasmodia have five major histone fractions, and we show by amino acid analysis, apparent molecular weight on three gel systems containing sodium dodecyl sulfate, mobility on gels containing Triton X-100, and other characterizations that these fractions are analogous to mammalian histones H1, H2A, H2B, H3, and H4. Significant differences between Physarum and mammalian histones are noted, with histone H1 showing by far the greatest variation. Histones H1 and H4 from Physarum microplasmodia have similar, but not identical, products of partial chymotryptic digestion compared with those of calf thymus histones H1 and H4. Labeling experiments, in vivo, showed that histone H1 is the major phosphorylated histone and approximately 15 separate phosphopeptides are present in a tryptic digest of Physarum histone H1. The core histones from Physarum, histones H2A, H2B, H3, and H4, are rapidly acetylated; histone H4 shows five subfractions, analogous to the five subfractions of mammalian histone H4 (containing zero to four acetyllysine residues per molecule); histone H3 has a more complex pattern that we interpret as zero to four acetyllysine residues on each of two sequence variants of histone H3; histones H2A and H2B show less heterogeneity. Overall, the data show that Physarum microplasmodia have a set of histones that is closely analogous to mammalian histones.

Chemical Phenomena↗
PubMed1983

Intranuclear localization of histone acetylation in Physarum polycephalum and the structure of functionally active chromatin.

Based on studies of histone acetylation in vivo in Physarum polycephalum, we present the following hypotheses: (1) Transcription-specific histone acetylation on histones H3 and H4 is a localized process at the nuclear matrix; (2) Histone acetylation in the S phase, which is specific for newly synthesized histones, occurs in an intranuclear nonlocalized process. These hypotheses can explain: (1) the histone specificity of histone acetylation that is dependent on the functional state of the chromatin; (2) the apparent absence of turnover of histone acetylation in the bulk of the chromatin despite a definite low level of steady-state acetylation of all four core histones in bulk chromatin; (3) the pattern of butyrate-induced hyperacetylation observed for active and inactive chromatin.

Acetates↗
PubMed1982

Thermal denaturation studies of acetylated nucleosomes and oligonucleosomes.

The thermal melting behaviors of control and acetylated mononucleosomes, dinucleosomes and trinucleosomes have been studied. Along each series of oligonucleosomes, the melting profiles change in a manner consistent with the increasing number of nucleosomes. For the control mononucleosome, the melting profile exhibits a premelting region at about 61-64 degrees C and a major cooperative transition at 75-77 degrees C. The melting profiles of the control dinucleosomes and trinucleosomes show a premelt at 61-62 degrees C (similar to that of the nucleosome core); an intermediate transition at 73-74 degrees C for the dinucleosome and at 76-77 degrees C for the trinucleosome and a major cooperative transition at 79-80 degrees C for the dinucleosome and at 81-82 degrees C for the trinucleosome. The major cooperative transition at the highest melting temperatures in the melting profiles of the mononucleosome, dinucleosome and trinucleosome comes from the melting of the central region of DNA in the nucleosome which complexed with the core histones; the premelt region is attributed to two DNA segments per nucleosome which flank this central DNA region and are free or weakly complexed with histones. The origin of the intermediate transition found for the dinucleosomes and trinucleosomes is not fully understood but probably results from the melting of DNA at the entry to and exit from the nucleosome and the linker DNA which are complexed with histones. A very similar pattern of behavior is observed for the acetylated oligonucleosomes. Direct comparison of the melting profiles of acetylated and control mononucleosomes, dinucleosomes and trinucleosomes show that the premelt region is unaffected by histone acetylation whereas the intermediate and major cooperative transitions for the acetylated oligonucleosomes are broader and occur consistently at lower temperatures than for the controls. These differences support proposals that the N-terminal regions of core histones interact within the nucleosome and on linker DNA.

Acetylation↗