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Biomedical subjects

L Hill

Publications and source records attributed to L Hill.

At least 109 records · Page 6Linked to original sources
PubMed1981

Effects of catecholamines and cyclic amp on excitation--contraction coupling in isolated skeletal muscle fibres of the frog.

1. In skeletal muscle the presence of a positive inotropic effect induced by adrenaline has been a matter of controversy. If it exists, it could be due to catecholamines acting on the actomyosin system, on the sarcoplasmic reticulum (SR) Ca2+ pump or on the release or influx of Ca2+. We investigated these possibilities by using intact, split and skinned skeletal muscle fibres. We also investigated whether adrenaline acts directly or through cyclic AMP. 2. Catecholamines produced an increase in twitch tension and in maximum rates of tension development and tension decay. The inotropic effect took 3 min to appear and 8 min to reach its maximum level. With tetanic stimulations the extra force appeared only at the beginning of the tetanus while approaching the same maximum level, and tended to disappear faster, the higher the frequency of stimulation. At 4 shocks/sec the peak twitch tension with catecholamines decreased during the first seven to ten twitches and became steady afterwards at a level that was still greater than the control. 3. Resting and action potentials showed no important changes in the presence of adrenaline that could explain the inotropic effect. 4. In split fibres the force produced with the release of Ca2+ from the SR by caffeine was 60-100% larger when cyclic AMP was added to the previous loading solution. In skinned fibres adrenaline given directly to the interior of the cell produced no changes in contraction--relaxation cycles induced by fixed amounts of Ca2+ applied with a pipette. 5. These results strongly suggest that catecholamines through cyclic AMP stimulate the SR Ca2+ pump, increasing thereby the concentration of Ca2+ within the SR. This extra Ca2+ when released during subsequent activation may produce the increase in twitch tension.

Action Potentials↗
PubMed1980

Human monoclonal antibody against Forssman antigen.

Hybrid cells formed between human lymphocytes and mouse myeloma cells produce human immunoglobulin in culture. Stable antibody-producing cell lines can be isolated after multiple cycles of low-density passage, cloning, and continued selection for immunoglobulin production. The origin and characteristics of a hybrid of human and mouse cells is described. This hybrid produces high concentrations (8.3 micrograms per milliliter) of human immunoglobulin M reactive with the terminal disaccharide of the Forssman glycolipid. These findings point to the potential use of human-mouse hybrid cells as a source of human monoclonal antibodies for therapeutic and diagnostic purposes.

Animals↗
PubMed1979

G1549, a new cyclic hydroxamic acid antibiotic, isolated from culture broth of Pseudomonas alcaligenes.

Antibiotic G1549, isolated from culture broth of Pseudomonas alcaligenes, is a new cyclic hydroxamic acid with a 1-hydroxy-2(1H)-pyridinone structure that complexes with metals. The structure of G1549 is suggested to be 1-hydroxy-5-methoxy-6-methyl-2(1H)-pyridinone. In vitro, G1549 and its copper and ferric complexes show moderate activity against Gram-positive bacteria, fungi and Trichomonas vaginalis. Topical application of G1549 and its copper and ferric complexes protect guinea pigs against cutaneous infection with Microsporum canis. The compounds, however, have some systemic toxicity in mice.

Animals↗
PubMed1979

Experiences with the tensor fascia lata flap.

Our experience with 60 TFL flaps is reviewed. The anatomy and the arcs of rotation of this flap are described. Our clinical experience--particularly in reconstruction of the groin and abdominal wall, and in free flap transfers--has been detailed, including the use of a free osteomyocutaneous sensory TFL flap for reconstruction of the heel.

Abdominal Muscles↗
PubMed1977

A-band length, striation spacing and tension change on stretch of active muscle.

1. Single muscle fibres of the frog were stretched during tetanus and filmed down the interference microscope. 2. Sarcomere lengths and A- and I-band widths were measured from cine films taken of the experimental sequences. 3. When a fibre was stretched during a tetanus, its A-band widths remained constant while its I-band widths changed according to the extent of the stretch. This behaviour is identical with that of a fibre stretched at rest. 4. Sarcomere lengths remained uniform along the fibre during a tetanus plus stretch, increasing as the I-band widths increased when the fibre was stretched. 5. At sarcomere lengths longer than LPmax (the length corresponding to greatest isometric tetanus tension) where the isometric tension diminishes as the fibre is lengthened, if the stretch was imposed during a tetanus the tension was higher after the stretch than before, showing a plateau which lasted for the duration of the tetanus. 6. This effect increased with longer sarcomere lengths and was not due to increased resting tension.

Animals↗
PubMed1977

Running amok.

This study examines twenty-four cases of amok, believed the largest number of cases ever collected. They were observed in Sarawak, East Malaysia. They occurred in all indigenous groups in Sarawak, excluding the Chinese, such as Malay, Sea Dayak, Land Dayak, Kayan, Punan and Melanau at frequencies more or less following the proportion of these groups in the total population. No differences were found according to religion, the Malay being Muslim and the other groups either predominantly Christian like the Iban or animistic. Only slight diminution in the frequency was observed from 1954 to 1968. The education level of the amok runners was much lower than that of the average population. The weapons used were those immediately at hand be it parang (short sword), ax, sticks, knives, guns, bare hands or a lorry. The classical four stages were largely present: (a) brooding and withdrawal, (b) homicidal paroxysm, (c) continuation of homicidal behaviour until killed, restrained or falling into stupor of exhaustion, (d) complete or partial amnesia. While in 14 no motive could be ascertained, insult, jealousy and paranoid ideation was present in the others. Both family history of mental illness and personal psychiatric history were predominant. All cases fell into accepted diagnostic categories from organic and endogenous psychosis to neurosis and behaviour disorder.

Adolescent↗
PubMed1976

Binding of nuclear triiodothyronine (T3) binding protein-T3 complex to chromatin.

Nuclear tirrodothyronine (T3) binding protein (NTBP)-T3 complex, prepared from liver nuclei of rats given [125I]T3 in vovo, rebinds to rat nuclear chromatin at pH 7.4 and at low, but not high, KCl concentrations. Liver NTBP-T3 complex binds to chromatin from liver, kidney, heart, brain, testis, and spleen. Binding was depressed at pH8, by addition of 10 mm CaCl2 or 100 mM MgCl2, and by 1 mM GTP or UTP. Although heart chromatin bound the most NTBP-T3 complex and brain the least, there is no clear separation of binding activity on comparison of three T3-responsive tissues (heart, liver, kidney) to the T3 insensitive tissues. Under the conditions of these experiments, there was no evident competition for binding sites on any of the six chromatins tested.

Animals↗
PubMed1976

Pharmacological investigations of virosecurinine.

This study reports some biological studies on the alkaloid virosecurinine isolated from the plant Securinega Virosa. Virosecurinine is an isomer of the securinine group of alkaloids present in plants used in traditional medicines in many areas, including the Central District of Papua New Guinea. Virosecurinine is mildly toxic to mice with an LD50 of 73 milligrams per kilogram body weight. Death results from violent tonic convulsions and paralysis similar to those observed with strychnine poisoning. Virosecurinine had no effect on the growth of the following bacteria, E. coli, S. aureus, and B. subtilis, or the fungi, F. monoliforme, P. viridicatum, A. niger, R. solani, R. stolonifer and C. lunata.

Alkaloids↗
PubMed1975

The specificity of oxidase and kinase preparations from Pseudomonas fluorescens towards deoxyfluoromonosaccharides.

With partially purified enzyme preparations from cell-free extracts of Pseudomonas fluorescens, 3-deoxy-3-fluoro-D-glucose and 3-deoxy-3-fluoro-D-gluconic acid are substrates for glucose oxidase (EC 1.1.3.4.) and gluconate dehydrogenase (EC 1.1.99.3), with K-m values 18.2 mM and 11.8 mM, respectively. The same enzymes that oxidize glucose and gluconic acid probably oxidize 3-deoxy-3-fluoro-D-glucose and 3-deoxy-3-fluoro-D-gluconic acid. The latter fluorinated carbohydrates and the presumed formation of 3-deoxy-3-fluoro-2-keto-D-gluconic acid, which has been isolated as a calcium salt and characterizied, are not substrates for gluconokinase (EC 2.7.1.12). Both 3-deoxy-3-fluoro-D-glucose and 3-deoxy-3-fluoro-D-gluconic acid act as competitive inhibitors of this enzyme preparation for gluconate, with K-i values 47.5 mM and 14.8 mM, respectively.

Alcohol Oxidoreductases↗