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Biomedical subjects

A Taylor

Publications and source records attributed to A Taylor.

At least 757 records · Page 42Linked to original sources
PubMed1981

The R gene product of bacteriophage lambda is the murein transglycosylase.

The radioactively labeled proteins synthesised in Escherichia coli minicells infected by bacteriophage lambda R and lambda R+ were compared by polyacrylamide gel electrophoresis. lambda R mutants, which have lost the ability to lyse host cells, lack a polypeptide of molecular weight 17.5 KD corresponding to the molecular weight of murein transglycosylase - a bacteriolytic enzyme from lambda lysates which we have described previously. It has been shown by direct comparison using radio-labeled enzyme that transglycosylase comigrates with the R gene product. The enzyme was undetectable in induced cultures of E. coli W3350 su degrees (lambda cI857 Ram 5) and C600 (lambda cI857 acR301), while it was present in a lambda Rz mutant lysate. We conclude that the transglycosylase is the R gene product.

Bacteriophage lambda↗
PubMed1981

Structure of chi hotspots of generalized recombination.

Chi recombinational hotspots are sites around which the rate of Rec-promoted recombination in bacteriophage lambda is elevated. Examination of a derivative of lambda into which the plasmid pBR322 was inserted reveals that pBR322 lacks Chi sites. Using this lambda-pBR322 hybrid, we obtained mutations creating Chi sites at three widely separated loci within pBR322. Nucleotide sequence analysis reveals that the mutations are single base-pair changes creating the octamer 5' GCTGGTGG 3'. This sequence is present at three previously analyzed Chi sites in lambda, and all analyzed mutations creating or inactivating these Chi sites occur within this octamer. We conclude that Chi is 5' GCTGGTGG 3', or its complement, or both.

Bacteriophage lambda↗
PubMed1981

Analysis of a predominant immunoglobulin population in the cerebrospinal fluid of a multiple sclerosis patient by means of an anti-idiotypic hybridoma antibody.

We have produced hybridoma antibodies directed against immunoglobulins present in the cerebrospinal fluid of a patient with multiple sclerosis (MS). One hybridoma antibody recognized an idiotypic determinant of an immunoglobulin population [an idiotype (Id)] which constituted approximately 1% of the immunoglobulin present in the cerebrospinal fluid. The Id focused in the pH range 8.0-8.4. It was present at roughly 10- to 15-fold higher relative (compared to total immunoglobulin) concentration in cerebrospinal fluid than in serum of the homologous MS patient. The Id could not be detected in three cerebrospinal fluid samples and 28 serum samples of heterologous MS patients or in the serum of 43 optic neuritis patients. The Id persisted in the homologous MS patient at increased concentration over the entire (6 years) observation period. The Id could be shown to react with a Theiler murine encephalomyelitis virus strain WW which was isolated from mice after inoculation with periplaque white matter from brain in a histologically confirmed case of MS.

Animals↗
PubMed1981

Gallium-67-citrate uptake in a case of acne vulgaris.

A case of increased Ga-67 uptake in a patient with active acne vulgaris is reported. The scan was requested in a search for metastatic testicular carcinoma or bleomycin pulmonary toxicity. Careful clinical evaluation including physical examination was necessary in order to avoid an erroneous scan interpretation.

Acne Vulgaris↗
PubMed1981

Studies on the biosynthesis of laminin by murine parietal endoderm cells.

The biosynthesis and processing of the polypeptides A (Mr = 450 x 10(3)), B1 (Mr = 240 x 10(3)), B2 (Mr = 230 x 10(3)) and C (Mr = 150 x 10(3)) of the extracellular matrix protein, laminin, were studied in murine parietal endoderm cells labelled with [35S]methionine. Various lines of evidence suggest that the A chains are not precursors to the smaller B chains. Firstly, the pulse-chase experiments, radioactivity in cytoplasmic A and (B1 + B2) chains declines with the same half-life of about 70 min. Secondly, peptide maps generated by digestion of A and B (B1 + B2) chains with Staphylococcus aureus V8 protease are different. Finally, rabbit antibodies to isolated, denatured (B1 + B2) chains do not cross-react with reduced and alkylated A chains. A, B1, B2 and C polypeptides are all glycosylated by an intracellular process involving the addition of tunicamycin and endo-beta-N-acetylglucosaminidase-H-sensitive N-linked oligosaccharide side chains. Further glycosylation probably occurs around the time of secretion. Disulphide bonding of some A and B chains can be observed in the cytoplasm within 10 min of adding [35S]methionine. However, it appears that some free A and B2 chains are present in the cytoplasm and that free A chains exist in the medium. The relationship between the 150 x 10(3)-Mr C glycoprotein and the A and B components is discussed. Although B and C chains generate different peptide maps after digestion with S. aureus V8 protease, antibodies raised against isolated, denatured C chains cross-react with reduced and alkylated B (but not A) chains. This suggests that B and C chains may share some antigenic determinant(s).

Animals↗
PubMed1981

Individual excitatory post-synaptic potentials due to muscle spindle Ia afferents in cat triceps surae motoneurones.

1. The monosynaptic projection of single Ia muscle spindle afferents to motoneurones of identified type has been examined by spike triggered averaging in barbiturate anaesthetized cats. 2. The amplitude of averaged individual monosynaptic e.p.s.p.s in medical gastrocnemius motoneurones from homonymous Ia afferents was clearly related to the motor unit mechanical properties. It was largest in type S units, intermediate in type FR and smallest in type FF. 3. The projection frequency of homonymous Ia afferents to medial gastrocnemius motoneurones followed the same order. 4. Similar trends were evident in both respects for the heteronymous projections of triceps surae. 5. The mechanical property of units which related most directly to e.p.s.p. size was muscle unit contraction strength, a single continuous relation existing throughout all three unit types. 6. On the basis of motor axon conduction velocity measurements, it appeared that motoneurone size could provide a simple explanation for e.p.s.p. size in type S and type FR units, but not in type FF. The latter had unduly small e.p.s.p.s relative to their axon conduction velocity, indicating a qualitatively different presynaptic organization for FF motoneurones from the others. 7. The data make it possible to predict that Ia afferent excitation alone would cause recruitment of units in order of increasing contraction strength and that this order would also obtain if a substantial part of the excitation came from other sources with uniform effect on all unit types. 8. It is shown that a consequence of the observed organization is that the gain of the Ia mediated stretch reflex would be approximately proportional to the developed force.

Animals↗
PubMed1981

Maintenance chrysotherapy in rheumatoid arthritis: a comparison of 2 dose schedules.

Maintenance treatment with chrysotherapy was given to 44 rheumatoid patients after a total of 1.0 g weekly injections of sodium aurothiomalate. 21 patients continued with 50 mg injections every 2 weeks, and 23 patients received the same dose at 4-week intervals. Their progress was followed over 1 year, after which time their clinical improvements were equally well sustained. Toxicity was greater in those patients receiving fortnightly injections. Five patients suffered a relapse after 8 months. These were not related to the frequency of injections nor to the serum gold levels. There appeared to be no advantage in maintenance injections at fortnightly intervals.

Adult↗
PubMed1981

Sequential cold-sensitive mutations in Aspergillus fumigatus. II. Analysis by the parasexual cycle.

From Aspergillus fumigatus I-21 (ATCC 32722), which grows at temperatures from 12 to 50 degrees C, three multistep, independently derived, cold-sensitive mutants unable to grow at 37 degrees C or below (Cs-37) were obtained by sequential exposure to ethylmethane sulfonate (strain AT2) or N-methyl-N'-nitro-N-nitrosoguanidine (AT1 and AT3). These mutants and ON5, a five-step Cs-37 mutant, were marked by mutations affecting spore color and nutritional requirements and crossed in four combinations by classical parasexual means. The heterokaryons demonstrated partial complementation with respect to auxotrophic requirements (suboptimal growth on minimal medium) and cold sensitivity (growth at 37 degrees C but not at 25 degrees C). Most presumed diploids, formed by exposure of the heterokaryons to d-camphor vapors, showed complete complementation but were unstable, as demonstrated by variations in spore sizes and markedly different ratios of segregant classes derived from different clones. Analysis of the segregants of the diploids or aneuploids, induced by Benomyl, indicated that multiple genes were responsible for cold sensitivity in each Cs-37 mutant, since segregants with various levels of cold sensitivity were obtained. The higher than predicted frequency of reversion to temperatures two or more steps back in the sequence of cold sensitivity mutations suggested that these genes or their products interacted. No Cs-37 segregant yielding a consistently lower frequency of revertants than the original mutants was obtained.

Aspergillus fumigatus↗
PubMed1981

Proprioceptive input from the jaw muscles and its influence on lapping, chewing, and posture.

Experiments are described which define criteria for identifying fusimotor axons discharging in filaments of the masseter nerve in lightly anaesthetized cats. During reflex movements of the jaw two patterns of discharge were observed in different fusimotor fibres. One type, called "sustained," fired at a fairly constant increased rate. The other, called "modulated," fired at high frequencies during the extrafusal muscle contraction. Evidence from spindle primary and secondary recordings in similar experiments strongly suggests that the "sustained" type were dynamic fusimotor fibres and the "modulated" type were static fusimotor fibres. New spindle recordings in normal unanaesthetized cats indicate that the modulated pattern of static fusimotor discharge also occurs in these conditions. Its effect is to reduce the tendency for spindle afferents to become silent during muscle shortening. A proposal is made that the static fusimotor discharge in cyclic movements may represent a temporal "template" for the intended movement as directed by the central pattern generator.

Animals↗
PubMed1981

Supernumerary mitral valve producing subaortic stenosis.

A ten-year-old girl with severe subaortic stenosis was found to have relatively mature valvular endocardial cushion tissue (fibromyxomatous sheets with a chorda tendinea attached to a left ventricular papillary muscle) immediately beneath the aortic valve. This structure behaved like a valve mechanism, obstructing the left ventricular outflow tract during ventricular systole. This anomaly is an extreme on the spectrum of obstructive endocardial cushion malformations.

Aortic Stenosis, Subvalvular↗
PubMed1981

Effect of 5-fluorouracil on the release of thymidine kinase from hepatoma cells in vitro.

Cells of the Morris hepatoma 7777 cultured in vitro have elevated levels of cytoplasmic thymidine kinase similar to those found in vivo. The cell-doubling time is slightly less than 24 hr. The addition of 5-fluorouracil to the culture medium (10 micrograms/ml) inhibits cell division, stimulates thymidine kinase production, and results in cell death which increases with time. Treated cells release significantly (p less than or equal to 0.01) more thymidine kinase into the culture medium than do untreated cells, and this effect can also be seen following a 60-min pulsed incubation of the cells with 5-fluorouracil. The total activity of thymidine kinase released is proportional to cell death and to the number of cells originally on the plate. These results suggest the possibility of monitoring tumor response to therapy in vivo by measuring serum levels of thymidine kinase.

Animals↗