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Biomedical subjects

M Knight

Publications and source records attributed to M Knight.

At least 19 recordsLinked to original sources
PubMed1992

Identification of a repetitive element in the snail Biomphalaria glabrata: relationship to the reverse transcriptase-encoding sequence in LINE-1 transposons.

BamHI-digested Biomphalaria glabrata DNA contains a repetitive 2.0-kb fragment which is readily discernible by ethidium bromide staining. We present evidence that this repetitive element is related at both the nucleotide and amino acid levels to long interspersed nuclear element (LINE)-like transposons. Although comparable elements have been described in several invertebrates, this is the first report of a molluscan homologue. In common with LINE transposons, an open reading frame in the B. glabrata element shows significant homology to reverse transcriptase--a feature believed to allow the dissemination of these elements in the eukaryotic genome.

Amino Acid Sequence↗
PubMed1992

Behavioural studies on WAY100289, a novel 5-HT3 receptor antagonist, in two animal models of anxiety.

The novel 5-HT3 receptor antagonist, WAY100289, was examined in two animal models of anxiety: the mouse two-compartment light: dark box, and the rat potentiated acoustic startle paradigm. The activity of WAY100289 in the light: dark box model was also compared with that of the selective 5-HT3 receptor antagonists ondansetron, zacopride, ICS-205,930 and quaternary ICS-205,930 (QICS). WAY100289 mimicked the activity profile of benzodiazepine positive controls in the mouse light: dark box, i.e. WAY100289 markedly and significantly increased the exploratory activity of mice in the more aversive light compartment, at doses of 0.01-1.0 mg/kg s.c. and 0.1-10.0 mg/kg p.o. Zacopride and ondansetron induced comparable effects at doses of 0.001-1.0 mg/kg s.c. ICS-205,930 displayed a markedly biphasic dose-response relationship; being active at 0.01 mg/kg s.c., but not at higher or lower doses. QICS was not active in the light: dark box up to a dose of 10 mg/kg s.c., suggesting that the compound does not enter the brain readily. WAY100289 was also active in the rat potentiated acoustic startle model, significantly attenuating the potentiated startle response at doses of 0.03 and 0.3 mg/kg s.c. The activity profile of WAY100289 in this model resembled that of ondansetron. These data strongly suggest that WAY100289 may possess anxiolytic properties in the clinic.

Analysis of Variance↗
PubMed1992

Countercurrent chromatography for the purification of peptides.

In Table 3 are listed the types of peptides separated by CCC, including the instruments used and the solvent conditions. In the last 20 years, intriguing discoveries about the hydrodynamic behavior of liquids in open-coiled tubing have introduced many possibilities for chromatographic separations. A fruitful area of endeavor certainly lies in further elucidation of the mechanisms. However, it is evident that CCC has the capability to separate all types of substances: organic compounds, proteins, membrane proteins, subcellular particles, as well as peptides, the intermediate-sized molecules. The potential for applications also lies at various levels of the scale such as analytical, laboratory, and, very importantly, industrial processes.

Chromatography, Liquid↗
PubMed1991

Purification of a synthetic myristylated peptide by counter-current chromatography.

A preparative purification of myristyl-Gly-Asn-Ile-Phe-Ala-Asn-Leu-Phe-Lys-Gly-Leu-Phe-Gly-Lys-Lys-Glu -NH2 was accomplished using the multi-coil counter-current chromatograph. A partition coefficient was determined in the n-butanol-acetic acid-water (4:1:5) system. Chromatographic runs were made in this system and one modified with ethyl acetate. The peptide material showed anomalous elution behavior due to its surfactant properties. It was found that by loading the sample exclusively in the stationary phase, satisfactory retention of the compound occurred. Finally, conditions utilizing the upper phase as the mobile phase successfully separated the impurities.

Amino Acid Sequence↗
PubMed1991

Schistosoma mansoni: use of a cloned ribosomal RNA gene probe to detect restriction fragment length polymorphisms in the intermediate host Biomphalaria glabrata.

Adult susceptibility of Biomphalaria glabrata to Schistosoma mansoni infection is controlled by simple Mendelian genetics. In this study a molecular approach was used to determine the degree of genetic variation between well-defined lines of B. glabrata which are either resistant (10-R2) or susceptible (M-line) to S. mansoni infection. A cloned probe pSM389, which contains part of the S. mansoni small ribosomal RNA gene and a portion of the nontranscribed spacer was found to cross-hybridize with B. glabrata DNA and was used in Southern hybridizations to detect restriction fragment length polymorphisms (RFLPs) between the above snail stocks. Polymorphisms were noted with a variety of restriction enzymes, namely Bg/II, BamHI, AccI, AvaII, ClaI, EcoRI, EcoRV, KpnI, PvuII, and NcoI. Although most RFLPs were relatively minor, a significant difference was observed with EcoRV. Further analysis of the EcoRV RFLPs among other isolates of the resistant stock demonstrated that a high frequency of genetic variation exists even among isolates of the same origin, but maintained in separate laboratories. Interestingly, RFLPs in the EcoRV site were detected in DNA isolated from a single generation of selfed progeny of a single 10-R2 parent. RFLPs associated with this site were found to occur between B. glabrata and B. tenagophila, B. straminea, and B. schrammi, indicating that Southern blot analysis using ribosomal gene probes may be useful for the molecular differentiation of B. glabrata from other intermediate hosts and from morphologically similar species that are refractory to infection.

Animals↗
PubMed1991

Effect of an incontinence training program on nursing home staff's knowledge, attitudes, and behavior.

To test a behavioral approach for urinary incontinence (UI), 166 staff in four nursing homes participated in a quasi-experimental study that measured knowledge and attitudes about UI and compliance with toileting protocols. The intervention group (N = 96) showed a slight increase in knowledge; their attitudes remained positive over the four testing times. Compliance with the more critical component of the toileting protocol was only 72%, although evidence existed that the protocol reduced UI. Results are discussed in terms of the sociocultural environment of nursing homes.

Female↗
PubMed1991

Evidence for distinct endothelin receptors in the pulmonary vascular bed in vivo.

The present study was undertaken to investigate the effects of endothelin (ET) isopeptides on the pulmonary vascular bed of the intact, spontaneously breathing cat under conditions of constant pulmonary blood flow and left atrial pressure. When pulmonary vasomotor tone was actively increased by intralobar infusion of U46619, intralobar bolus injections of ET-1 (1 micrograms), ET-2 (1 micrograms), and ET-3 (3 micrograms) produced marked reductions in pulmonary and systemic vascular resistances. The pulmonary vasodilator response to each ET isopeptide was not altered by atropine (1 mg/kg i.v.), indomethacin (2.5 mg/kg i.v.), or ICI 118551 (1 mg/kg i.v.), but was significantly inhibited by an intra-arterial (i.a.) infusion of glybenclamide at 5 mg/kg. This dose of glybenclamide significantly inhibited the decrease in lobar arterial and systemic arterial pressures in response to intralobar injection of pinacidil (30 and 100 micrograms), whereas the pulmonary vasodilator responses to acetylcholine (0.03 and 0.1 micrograms) and prostaglandin I2 (0.1 and 0.3 micrograms) were not altered. The systemic vasodilator response to each ET isopeptide was not changed by glybenclamide or by the other blocking agents studied. The present data demonstrate for the first time that ET-1, ET-2, and ET-3 dilate the pulmonary vascular bed in vivo. The present data suggest that the pulmonary vasodilator response to ET isopeptides depends, in part, on activation of potassium channels and is mediated differently from the systemic vasodilator response to these substances. Contrary to earlier work, the present data indicate the pulmonary vascular response to ET isopeptides depends on the pre-existing level of pulmonary vasomotor tone. Furthermore, the present data suggest that in the lung ET-1, ET-2, and ET-3 may serve as endogenous agonists for potassium channels, a newly described vasodilator mechanism in the pulmonary vascular bed of intact adult animals.

Animals↗
PubMed1991

Direct evidence for an important species difference in the mechanism of 8-OH-DPAT-induced hypothermia.

1. Parallel series of experiments were carried out in the rat and mouse in order to investigate the mechanism(s) underlying the hypothermia induced in rodents by the selective 5-HT1A receptor agonist, 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT). 2. In the mouse, lesioning of central 5-hydroxytryptaminergic neurones (by use of the neurotoxin, 5,7-dihydroxytryptamine; 5,7-DHT) abolished the hypothermic response to 8-OH-DPAT, and depletion of brain 5-hydroxytryptamine (5-HT) levels (with the 5-HT synthesis inhibitor, p-chlorophenylalanine) markedly attenuated the response in this species. These pretreatments did not significantly attenuate 8-OH-DPAT-induced hypothermia in the rat, except for a significant attenuation of the response in 5,7-DHT-lesioned rats at the top dose of 8-OH-DPAT (1.0 mg kg-1, s.c.). 3. Pharmacological pretreatments which facilitate 5-HT release (selective 5-HT uptake inhibitors, precursor (5-hydroxytryptophan) loading, or fenfluramine), markedly attenuated or abolished 8-OH-DPAT-induced hypothermia in the mouse. These pretreatments generally had no significant effect on 8-OH-DPAT-induced hypothermia in the rat. 4. The selective noradrenaline uptake inhibitor, desipramine, had no effect on the hypothermic response to 8-OH-DPAT in either species. The selective dopamine uptake inhibitor, nomifensin, significantly increased the hypothermic response to 8-OH-DPAT in the mouse, but did not affect the response in the rat except at high, motor stimulant doses, when the response was attenuated. 5. These data are consistent with the hypothesis that 8-OH-DPAT-induced hypothermia is mediated by presynaptic autoreceptors in the mouse and by postsynaptic 5-HT1A receptors in the rat. Preliminary data also indicate an involvement of dopamine release in the mouse but not in the rat.

5,7-Dihydroxytryptamine↗
PubMed1991

Use of activated charcoal to reduce elevated serum phenobarbital concentration in a neonate.

The course of a neonate administered activated charcoal orally for elevated phenobarbital concentration is described. The neonate required a serum concentration of phenobarbital eventually exceeding 80 micrograms/mL for seizure control. However, due to the severe CNS injury as a result of the asphyxia at birth, a diagnosis of cerebral death by electroencephalogram and apnea test was pursued. This required the phenobarbital concentration to be less than 30 micrograms/mL. Serial phenobarbital concentrations during this time indicated a 250 hour half-life, which would require two weeks for the phenobarbital to drop below 30 micrograms/mL. With the administration of six doses of activated charcoal at 0.7 g/kg/dose, the phenobarbital serum concentration decreased to 22 micrograms/mL, giving an estimated phenobarbital half-life of 22 hours. This, and two other subsequent cases, indicates repeated doses of activated charcoal are effective in augmenting the clearance of certain drugs in the neonatal age group.

Administration, Oral↗
PubMed1991

Neonatal seizures.

The clinician caring for newborn infants must be aware of the clinical implications of a seizure in a neonate. The diagnostic possibilities are many including generalized, systemic conditions in addition to central nervous system problems. It is important for the clinicians to be able to distinguish nonepileptic abnormal neurologic findings from seizures requiring anticonvulsant therapy. The decision to treat with anticonvulsants must be based on a comprehensive evaluation of the infant excluding secondary, self-limiting courses of seizures. Anti-convulsant therapy is a significant commitment so the clinician must be familiar with the drugs to be used.

Anticonvulsants↗
PubMed1989

Purification of synthetic peptides on a high-resolution preparative reversed-phase column.

A 2-in. I.D. column filled with 10-microns spherical C18 bonded silica with 120 A pores was used for the preparative purification of various synthetic peptides in one step. The small-sized silica packing afforded high resolution and the spherical shape helped maintain a relatively low back-pressure during the chromatography. Conditions for performing the separations were derived from the analytical chromatography of samples on a column of similar 5-microns material. The same amount of organic modifier, but with the gradient duration increased, achieved very similar separations on the preparative column.

Amino Acid Sequence↗
PubMed1989

Chromatography of peptides on a multi-coil counter-current chromatograph.

A modified horizontal flow-through coil planet centrifuge has been constructed that has the potential for preparative chromatography. The multi-coil counter-current chromatograph, equipped with a set of four multi-layer coils, has have improved performance with polar solvents suitable for peptide elution. Separations of a group of dipeptides and purification of a cholecystokinin fragment and an undecapeptide were achieved with n-butanol-acetic acid-water at high flow-rates with good resolution.

Cholecystokinin↗
PubMed1989

Predicted structure of a major Schistosoma mansoni eggshell protein.

The complete sequence for a major Schistosome mansoni eggshell protein gene has been determined from a genomic DNA fragment. The use of an open reading frame encoding a glycine-rich polypeptide was confirmed by in vitro translation of schistosome mRNA in the presence of [3H]glycine and comparison with the amino acid composition of purified, schistosome eggshells. Apart from the extraordinary abundance of glycine and tyrosine which are evenly distributed throughout the polypeptide chain, the most striking features of the deduced amino acid sequence are the presence of five well-conserved tandem repeats of 16-18 residues in the N-terminal region and the asymmetrical distribution of charged residues. Acidic residues (Asp) are confined to the N-terminal region, while basic residues (Lys, His), with the exception of a single histidine, are found in the C-terminal region. A model structure composed of short anti-parallel beta-strands is proposed, in which glycines and residues with small side chains lie within the strands and tyrosines and cysteines are arranged at the bends, where they would be available for cross-linking. Four such strands form one of the tandem repeats which are predicted in turn to form a stack of five closely packed beta-sheets, each of three strands and linked by the more variable fourth strand. The C-terminal region may form a similar but less compact structure. The ordered structure demonstrated by birefringence studies of the schistosome eggshell [Kusel, J. (1970) Parasitology 60, 79-88] could be formed by packing of the polypeptides such that the N-terminal domain contributes counter ions or cross-links to the C-terminal domain of adjacent molecules.

Amino Acid Sequence↗
PubMed1989

A cDNA clone encoding part of the major 25,000-dalton surface membrane antigen of adult Schistosoma mansoni.

Immunoscreening of an adult Schistosoma mansoni cDNA expression library, using antibodies raised against purified adult worm tegumental surface membranes, identified a recombinant clone containing a 141-bp insert. Antibodies raised against the recombinant antigen bound specifically to the tegument of adult worms and immunoprecipitated the major 25,000-dalton surface membrane antigen as well as a 22,000-dalton nascent polypeptide generated by cell-free translation of adult S. mansoni mRNA. The mature 25,000-dalton antigen was found to be precipitated by antibodies from infected mice, rats and humans.

Amino Acid Sequence↗
PubMed1988

Scale-up methodology for the preparative purification of peptide M.

An octadecapeptide, peptide M, the epitope of a retinal protein that induces experimental autoimmune uveitis, was synthesized and purified by preparative reversed-phase chromatography. The flow-rate and gradient conditions for maximum separation of impurities were determined on a 30 x 0.39 cm I.D. column of Delta Pak (15-microns spherical C18-bonded silica with 300-A pores). The maximum amount of peptide that was resolved under these conditions was then determined experimentally. Using a scale factor dependent on the square of the column diameters, the flow-rate and amount loaded were increased 164 times on a 30 x 5 cm I.D. column of the same packing. The same resolution was achieved. Batches of 200-342 mg were chromatographed with reproducible results, providing a total yield of 394 mg of pure peptide.

Chromatography, High Pressure Liquid↗
PubMed1988

Reversed-phase preparative chromatography of [D-Ala1]-peptide T amide.

[D-Ala1]peptide T amide is a metabolically stable and more potent analogue of peptide T, a proposed inhibitor of human immunodeficiency viral infectivity of human T-cell lymphocytes. The peptide was synthesized by solid-phase methods to provide amounts of several grams. The product was purified by chromatography on a 25 cm x 2 in. column of DuPont Zorbax Pro-10 C8 (10 micron) packing. Sample loads of 100-450 mg were chromatographed isocratically in 0.1% trifluoroacetic acid and 5% acetonitrile at a flow-rate of 110 ml/min. Under these conditions, the pure peptide fraction was eluted reproducibly between 15 and 22 min. After solvent removal and lyophilization, the recovery of pure peptide was 50% by weight.

Chemical Phenomena↗