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Biomedical subjects

M Richardson

Publications and source records attributed to M Richardson.

At least 289 records · Page 16Linked to original sources
PubMed1991

Complementation of snf1, a mutation affecting global regulation of carbon metabolism in yeast, by a plant protein kinase cDNA.

A cDNA, cRKIN1, encoding a putative homologue of the yeast (Saccharomyces cerevisiae) SNF1-encoded protein-serine/threonine kinase, has been isolated from a library prepared from rye endosperm mRNA. Northern blot analysis demonstrated the presence of cRKIN1-related transcripts in developing endosperms but not in shoots, and Southern blot analysis showed the presence of a small gene family. SNF1 plays a central role in carbon catabolite repression in yeast and expression of the RKIN1 sequence in yeast snf1 mutants restored SNF1 function. This suggests that the RKIN1 protein has a role in the control of carbon metabolism in endosperms of rye.

Amino Acid Sequence↗
PubMed1991

The complete amino acid sequence of the haemorrhagic factor LHFII, a metalloproteinase isolated from the venom of the bushmaster snake (Lachesis muta muta).

The complete amino acid sequence the haemorrhagic agent LHFII, a Zn and Ca containing metalloproteinase isolated from the venom of the Bushmaster snake Lachesis muta muta was determined by automated and DABITC/PITC microsequencing of the intact protein, fragments derived by cleavage with cyanogen bromide, and peptides resulting from enzymatic digestions with trypsin and the protease from S. aureus V8. The protein is composed of 200 residues and exhibits considerable sequence homology with the haemorrhagic toxins from a number of other snake venoms, and some metalloproteinases in the region of the putative Zn-binding sites.

Amino Acid Sequence↗
PubMed1991

Characteristics of thrombin-degranulated human platelets: development of a method that does not use proteolytic enzymes for deaggregation.

A method has been developed for preparing suspensions of washed human platelets that have lost as much as 90% of their dense granule and alpha granule contents as a result of stimulation by thrombin (0.9 U/ml for 3 min at 37 degrees C), and recovering the platelets without using a proteolytic enzyme. Glycyl-L-prolyl-L-arginyl-L-proline (GPRP) was used to prevent polymerization of released fibrinogen and arginyl-glycyl-aspartyl-serine (RGDS) to block the interaction of released fibrinogen, vWf or fibronectin with the glycoprotein IIb/IIIa complex. The thrombin used to degranulate the platelets was neutralized with D-phenylalanyl-L-prolyl-L-arginine chloromethyl ketone (FPRCH2Cl) and prostaglandin E1 was added to return the platelets towards a disc shape. The degranulated platelets aggregated in response to ADP, platelet activating factor, arachidonate and the thromboxane A2 mimetic, U46619 in the presence of added fibrinogen; the platelets changed shape but did not aggregate in response to collagen. Thrombin and the calcium ionophore, A23187, caused aggregation without added fibrinogen. Synergism between pairs of aggregating agents at low concentrations was observed. Little TXB2 was formed when the platelets were reaggregated by thrombin. RGDS and F(ab')2 fragments of an antibody to fibrinogen inhibited reaggregation induced by thrombin and A23187 indicating that small amounts of fibrinogen at the platelet surface may support aggregation by strong agonists. Adherence of thrombin-degranulated platelets to a collagen-coated surface was less than for controls, but spreading was more extensive. Electron-microscopic immunogold cytochemistry with anti-human fibrinogen IgG showed numerous gold particles in platelet vacuoles.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Diphosphate↗
PubMed1991

A new family of small (5 kDa) protein inhibitors of insect alpha-amylases from seeds or sorghum (Sorghum bicolar (L) Moench) have sequence homologies with wheat gamma-purothionins.

Three isoinhibitors of locust and cockroach gut alpha-amylases were purified from seeds of sorghum by saline extraction, precipitation with ammonium sulphate, affinity chromatography on Red-Sepharose and preparative RP-HPLC on Vydac C18. The complete primary structures were determined by automatic degradation of the intact reduced and S-alkylated proteins, and by manual DABITC/PITC microsequencing of peptides obtained from enzyme digests. The inhibitors consist of 47 (SI alpha-1) or 48 (SI alpha-2, ST alpha-3) amino acids, and are the smallest plant inhibitors of alpha-amylase currently known. The sequences of the three isoinhibitors exhibit between 38% and 87% identity among themselves and also have homology (32-81%) with the gamma-purothionins recently isolated from wheat endosperm.

Amino Acid Sequence↗
PubMed1991

Recurrent bronchogenic cyst. An argument for complete surgical excision.

A case of a recurrent bronchogenic cyst in a 42-year-old woman 25 years after original resection led to a review of the therapeutic modalities for the management of bronchogenic cysts. Recurrence of bronchogenic cysts is a reason for complete surgical excision of symptomatic bronchogenic cysts at initial presentation. If either asymptomatic or symptomatic bronchogenic cysts are drained or partially excised, long-term follow-up is indicated to detect recurrence.

Adult↗
PubMed1991

Comparison of the amino acid sequences of the lectins from seeds of Dioclea lehmanni and Canavalia maritima.

The amino acid sequences of the major lectins from the seeds of Dioclea lehmanni and Canavalia maritima were determined by DABITC/PITC microsequence analysis of peptides derived from the proteins by enzymatic digestions with trypsin, chymotrypsin and the protease from S. aureus V8. These sequences were found to be very similar to those of the lectins from Dioclea grandiflora and Canavalia ensiformis (Con A). The D. lehmanni lectin was unusual amongst legume lectins in that it contained a single Cys.

Amino Acid Sequence↗
PubMed1991

Chymotrypsin treatment increases the activity of Clostridium perfringens enterotoxin.

Chymotrypsin treatment of the enterotoxin from Clostridium perfringens results in the loss of 36 amino acids from the N-terminus and 3 amino acids from the C-terminus. This processing results in a 3.2 fold increase in activity on Vero cells, which is close to what had been found for trypsin treatment following the loss of 25 amino acids from the N-terminus.

Amino Acid Sequence↗
PubMed1991

The complete amino acid sequence of the major Kunitz trypsin inhibitor from the seeds of Prosopsis juliflora.

The major inhibitor of trypsin in seeds of Prosopsis juliflora was purified by precipitation with ammonium sulphate, ion-exchange column chromatography on DEAE- and CM-Sepharose and preparative reverse phase HPLC on a Vydac C-18 column. The protein inhibited trypsin in the stoichiometric ratio of 1:1, but had only weak activity against chymotrypsin and did not inhibit human salivary or porcine pancreatic alpha-amylases. SDS-PAGE indicated that the inhibitor has a Mr of ca 20,000, and IEF-PAGE showed that the pI is 8.8. The complete amino acid sequence was determined by automatic degradation, and by DABITC/PITC microsequence analysis of peptides obtained from enzyme digestions of the reduced and S-carboxymethylated protein with trypsin, chymotrypsin, elastase, the Glu-specific protease from S. aureus and the Lys-specific protease from Lysobacter enzymogenes. The inhibitor consisted of two polypeptide chains, of 137 residues (alpha chain) and 38 residues (beta chain) linked together by a single disulphide bond. The amino acid sequence of the protein exhibited homology with a number of Kunitz proteinase inhibitors from other legume seeds, the bifunctional subtilisin/alpha-amylase inhibitors from cereals and the taste-modifying protein miraculin.

Amino Acid Sequence↗
PubMed1991

Pressor effects of caffeine and cigarette smoking.

Pressor effects of caffeine and cigarette smoking were examined in 15 normotensive young men and women. A cross-over design was used in which all subjects participated in four separate conditions: placebo alone, caffeine alone, placebo plus smoking, and caffeine plus smoking. Caffeine and smoking produced independent increases in systolic and diastolic blood pressure, and these effects were additive in the caffeine-plus-smoking condition. Heart rate was significantly increased by smoking but was essentially unaffected by caffeine.

Adolescent↗
PubMed1991

Predictive value of oropharyngeal cultures for identifying lower airway bacteria in cystic fibrosis patients.

Identifying lower respiratory pathogens in young, non expectorating cystic fibrosis (CF) patients has been problematic. Bronchial secretions are difficult to obtain, and little is known about lower airway flora in these patients. We collected simultaneous bronchial and oropharyngeal specimens in 43 CF patients in optimal respiratory status, including both expectorating (17) and nonexpectorating (26) patients, to determine the predictive value of oropharyngeal cultures for identifying lower airway pathogens. An additional goal was to characterize the lower respiratory flora of these patients. Predictive values were defined as the proportion of oropharyngeal culture results that accurately reflected the results of bronchial cultures. Predictive values of positive oropharyngeal cultures in nonexpectorating patients were 83% (95% confidence interval 36 to 100%) for Pseudomonas aeruginosa and 91% (59 to 100%) for Staphylococcus aureus. Predictive values of negative oropharyngeal cultures were lower: 70% (48 to 86%) for R aeruginosa and 80% (52 to 96%) for S. aureus. A relatively high proportion of nonexpectorating CF patients less than 10 yr old had R aerusginosa (11 of 24, 46%) or Klebsiella species (5 of 24, 21%) in their lower airways. The isolation of Klebsiella was associated with younger age (p = 0.03) and recent administration of antistaphylococcal antibiotics (p = 0.05). Our results suggest that oropharyngeal cultures yielding R aeruginosa or S. aureus are highly predictive, but such cultures lacking these organisms do not rule out the presence of these pathogens in the lower airways of CF patients.

Bacterial Infections↗
PubMed1990

A new protein inhibitor of trypsin and activated Hageman factor from pumpkin (Cucurbita maxima) seeds.

A protein inhibitor (CMTI-V; Mr 7106) of trypsin and activated Hageman factor (Factor XIIa), a serine protease involved in blood coagulation, has been isolated for the first time from pumpkin (Cucurbita maxima) seeds by means of trypsin-affinity chromatography and reverse phase high performance liquid chromatography (HPLC). The dissociation constants of the inhibitor complexes with trypsin and Factor XIIa have been determined to be 1.6 x 10(-8) and 4.1 x 10(-8) M, respectively. The primary structure of CMTI-V is reported. The protein has 68 amino acid residues and one disulfide bridge and shows a high level of sequence homology to the Potato I inhibitor family. Furthermore, its amino terminus consists of an N-acetylates Ser. The reactive site has been established to be the peptide bond between Lys44-Asp45. The modified inhibitor which has the reactive site peptide bond hydrolyzed inhibits trypsin but not the Hageman factor.

Amino Acid Sequence↗
PubMed1990

The purification and amino acid sequence of the lethal neurotoxin Tx1 from the venom of the Brazilian 'armed' spider Phoneutria nigriventer.

A lethal neurotoxic polypeptide of Mr 8 kDa was purified from the venom of the South American 'armed' or wandering spider Phoneutria nigriventer by centrifugation, gel filtration on Superose 12, and reverse phase FPLC on columns of Pharmacia PepRPC and ProRPC. The purified neurotoxin Tx1 had an LD50 of 0.05 mg/kg in mice following intracerebroventricular injection. The complete amino acid sequence of the neurotoxin was determined by automated Edman degradation of the native and S-carboxymethylated protein in pulsed liquid and dual phase sequencers, and by the manual DABITC/PITC double coupling method applied to fragments obtained after digestions with the S. aureus V8 protease and trypsin. The neurotoxin Tx1 consists of a single chain of 77 amino acid residues, which contains a high proportion of cysteine. The primary structure showed no homology to other identified spider toxins.

Amino Acid Sequence↗
PubMed1990

Relationship between vessel wall 13-HODE synthesis and vessel wall thrombogenicity following injury: influence of salicylate and dipyridamole treatment.

We performed studies to determine the relationship between injured vessel wall thrombogenicity, vessel wall 13-hydroxyoctadecadienoic acid (13-HODE) synthesis and cAMP levels in rabbit treated with salicylate or dipyridamole. Injured vessel wall thrombogenicity was measured as the number of 3H-adenine labelled platelets adhered to the subendothelial basement membrane exposed by air injury in carotid arteries of rabbits treated orally with salicylate or dipyridamole. Vessel wall 13-HODE was measured by HPLC and vessel wall cAMP was measured by RIA. Vessel wall thrombogenicity was increased two-fold in rabbits treated with salicylate and decreased by half in rabbits treated with dipyridamole. The levels of vessel wall cAMP levels were correlated both with the plasma dipyridamole levels and increases in 13-HODE synthesis. cAMP levels were unaffected by salicylate treatment, but 13-HODE synthesis was decreased. We conclude that there is a significant relationship between vessel wall cAMP levels and 13-HODE synthesis, which in turn, influences subsequent vessel wall thrombogenicity.

Animals↗
PubMed1990

The relation among vessel injury, thrombus formation, and platelet survival in rabbits.

Continuous or repeated injury of rabbit aortae by indwelling vascular catheters caused the deposition of platelets on the injured vessels and the formation of thrombi rich in platelets and fibrin at sites where flow was most disturbed and injury was most extensive. Incorporation of 51Cr platelets into the thrombi reached a maximum between 3 and 24 hr. The platelet-fibrin-rich thrombi remained reactive to circulating platelets for at least 14 days. Continuing reactivity of thrombi and the turnover of platelets in the thrombi were accompanied by an increase in the proportion of platelets that separated in the least dense fraction on Stractan density gradients. Platelet survival was also shortened (43.5 +/- 5.9 hr in animals with catheters, compared with 62.6 +/- 4.5 hr in animals with a sham operation), indicating that some platelets that had taken part in thrombus formation or had interacted with the injured vessel wall were rapidly cleared from the circulation. Platelets from rabbits that had had indwelling aortic catheters in place for 3 or 6 days survived significantly longer than those from animals with a sham operation upon injection of the platelets into normal animals; thus, continuous turnover of platelets on injured vessels and thrombi, and the clearance of altered platelets, leads to a population of younger platelets that survive longer. The continuing reactivity of thrombi may in part account for repeated occlusive episodes in vascular disease. The contribution of thrombin generation and fibrin formation to the platelet-rich thrombi is substantial and warrants the ongoing evaluation of treatment with a combination of anticoagulant and antiplatelet agents in arterial thrombosis and in thrombus formation on vascular catheters.

Animals↗