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Biomedical subjects

L Drake

Publications and source records attributed to L Drake.

8 recordsLinked to original sources
PubMed1994

The major secreted product of the whipworm, Trichuris, is a pore-forming protein.

The data presented here describe the first unequivocable characterization of a pore-forming protein in any helminth parasite. The excretory/secretory (E/S) material of the human whipworm T. trichiura contains a highly abundant protein of molecular mass 47 kDa (TT47); the murine model parasite, T. muris, contains a similarly abundant protein of molecular mass 43 kDa (TM43). When purified to homogeneity, these proteins induce ion-conducting pores in lipid bilayers. Antibodies raised against TM43 abolish channel activity. Pore formation in epithelial cell membranes may facilitate invasion of the host gut by Trichuris and enable the parasite to maintain its syncytial environment in the caecal epithelium. The observation that this activity may be inhibited by antibody opens a possible avenue for drug and vaccine development.

Animals↗
PubMed1992

Detection of peptidases in Trypanosoma cruzi epimastigotes using chromogenic and fluorogenic substrates.

Detergent extracts of Trypanosoma cruzi epimastigotes catalysed the hydrolysis of a range of amino-acyl and peptidyl p-nitro-anilides and aminomethylcoumarins. At least three enzymes were detected that cleave Z-Phe-Arg-MCA. Two of these were optimally active at alkaline pH, the other at pH 4.0. Of the two enzymes with alkaline pH optima, one was a cysteine peptidase and was unable to cleave Bz-Arg-MCA readily, whilst the other cleaved Bz-Arg-MCA and was inhibited by diisopropyl fluorophosphate. The acidic enzyme was similar to cathespin L of other eukaryotes with respect to its pH profile, substrate-specificity and inhibitor-sensitivity. Evidence was presented that epimastigotes contain a cysteine-type dipeptidyl aminopeptidase, one or more aminopeptidases, and a serine peptidase that cleaves Boc-Ala-Ala-pNA. Digitonin solubilization of the activities from cells supports the hypothesis that the cathespin L-like enzyme and the dipeptidyl aminopeptidase are lysosomal, whilst the Bz-Arg-MCA hydrolase, the aminopeptidases and the Boc-Ala-Ala-pNA serine peptidase are cytosolic.

Amino Acid Sequence↗
PubMed1992

A useful modification of cDNA that enhances purification of recombinant protein.

With the availability of new and improved DNA vectors for producing large amounts of proteins by recombinant DNA technology, there is a growing need for efficient recovery of the desired protein, often from liters of culture medium. In this report, we describe a relatively simple modification of recombinant cDNA, that, in combination with immobilized metal affinity chromatography, is a rapid, inexpensive and highly effective method for enriching or purifying a desired protein.

Base Sequence↗
PubMed1984

Effects of sulfonylureas on the actions of insulin and insulin-mimickers: potentiation of stimulated hexose transport in adipocytes.

The sulfonylurea glyburide, a 'second-generation' oral hypoglycemic compound, was studied in vitro in order to determine its cellular mechanism of action in adipocytes prepared from cultured rat epididymal fat tissue. Glyburide treatment (1 microgram/ml) for 20 h did not alter insulin receptor number or affinity, or down-regulation by insulin. Biologic responses of these cells were measured in the presence of insulin or the oxidants Vitamin K5 and H2O2, which have insulin-like activity, but do not act through the binding portion of the receptor. 2-Deoxyglucose uptake was not significantly changed by exposure to glyburide alone. However, the sulfonylurea increased the insulin-stimulated or insulin-mimicker-activated uptake by approximately 30%. Insulin-stimulated glucose oxidation was also potentiated when glucose transport was rate limiting for metabolism. These findings extend our earlier observation that in adipose tissue the primary cellular mechanism of action of sulfonylureas is to potentiate insulin-stimulated hexose transport, and that this process may account for their hypoglycemic activity.

Adipose Tissue↗
PubMed1981

ties"ties".

The diagnostic category of learning disabilities is a heterogeneous one, but few empirical attempts have been made to distinguish subgroups. Recent research, however, suggests that it may be meaningful to discriminate between "hyperactive" and "nonhyperactive" learning-disabled children. In the present study, 21 learning-disabled children identified as "hyperactive" through teacher nominations and ratings were compared to 15 learning-disabled children identified as "nonhyperactive" in the same manner. The two groups differed on rated behavior, birth order, amount of prescribed stimulant medication, amount of psychosocial stress, and Verbal, Performance, and Full Scale WISC-R IQ scores. They did not differ, however, on several demographic variables, the number of perinatal complications, reading achievement, and a number of tonic and phasic measures of autonomic activity. These findings support the distinction between "hyperactive" and "nonhyperactive" subgroups of learning-disabled children, but suggest that the two subgroups may have a similar biological substrate.

Attention Deficit Disorder with Hyperactivity↗
PubMed1978

Treatment of alopecia areata with dinitrochlorobenzene.

Persistent refractory alopecia areata in 26 patients was treated topically with dinitrochlorobenzene (DNCB). Sixteen patients have had excellent regrowth of hair; three patients could either not be initially sensitized or an adequate allergic contact dermatitis on the scalp did not develop. Two patients discontinued therapy within two months; hair growth did not develop in five patients despite an adequate trial. Augmentation of the T-lymphocyte pool via DNCB sensitization and challenge may become effective therapy for some patients with severe alopecia areata.

Administration, Topical↗
PubMed1975

Effect of amygdalectomy on habituation and CER in rats.

Amygdalectomized, Sham operates and unoperated rats received 20 habituation trials followed by CER training during which the habituation stimulus was made a CS for 10 CS-UCS pairings. Although no reliable differences in rate of magnitude of habituation as measured by suppression ratio magnitudes and ITI durations were apparent between any groups, these same measures indicated that substantial deficits in conditioned suppression were produced by bilateral amygdalectomy. In addition the lesion produced a reliable deficit in unconditioned suppression and a slight but reliable reduction in the number of ccs of water consumed in a 24 hour period. These results are more consistent with the hypothesis that amygdalectomy interferes with the arousal of fear than with the proposals that this lesion produces deficits in habituation or in response inhibition.

Amygdala↗