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Biomedical subjects

P Martin

Publications and source records attributed to P Martin.

At least 937 records · Page 52Linked to original sources
PubMed1980

Kinetic studies on the action of Mucor pusillus, Mucor miehei acid proteases and chymosins A and B on a synthetic chromophoric hexapeptide.

The action of two milk-clotting fungal proteases from Mucos pusillus and Mucor miehei and of chymosins A and B on the hexapeptide, Leu-Ser-Phe(NO2)-Nle-Ala-Leu-OMe, and on kappa-casein were studied. The effects of pH and temperature on the initial rates of hydrolysis of the hexapeptide were examined. Crystalline chymosin and M. pusillus protease exhibited optimal activities around 49 and 55 degrees C, respectively, whereas the optimum temperature for M. miehei protease is higher than 63 degrees C. The optimum pH was about 4.7 for both fungal proteases whereas chymosin A and chymosin B exhibited optimal activities around 4.2 and 3.7, respectively. Kinetic parameters were then determined under optimal conditions and/or at pH 4.7. Fungal proteases had kcat/Km ratios that were similar to each other and that were significantly greater than the ratios obtained for the chymosins. Nevertheless, chymosins had much greater clotting activities towards kappa-casein relative to their proteolytic activities towards the synthetic peptide.

Caseins↗
PubMed1980

Eau de Javel and prevention of chromate allergy in France.

"Eau de Javel" (liquid bleach) is a common cause of chromate contact allergy. A historical review explains the reasons for the addition of sodium dichromate after the First World War. The chromium content in different brands of eau de Javel has been determined by flameless atomic absorption spectrophotometry. The results indicate that the chromium content is very low (0.03--3.65 mg/l) in French brands, whereas it is still important (7.06--82.9 mg/l) in Belgian brands, such an observation indicates that the almost complete removal of chromate in most brands of French eaux de Javel is a good example of prevention in the field of contact dermato-alllergology.

Belgium↗
PubMed1980

Comparative study of the density of particles in suspensions for patch testing.

A simple and reliable method to evaluate the density of particles in patch test suspensions is described. The number of particles per unit volume has been found to vary significantly within a wide range of values. These variations have no relation to the concentration or the molecular weight of the substance, as far as particles larger than 10 micron are concerned. Because the presence of particles is one of the factors which can influence percutaneous penetration and since physical manipulations are able to modify the size of these particles, it is suggested that the kinetics of penetration of haptens through the skin should be revaluated with regard to this special point.

Absorption↗
PubMed1980

Atrial inotropic responses to brief vagal stimuli: frequency-force interactions.

The effect of brief vagal stimulus burst on atrial contractile force was assessed in paced- and unpaced-heart preparations by recording the changes in pressure (AP) generated in a balloon in the right atrial appendage or by a miniature strain gauge on the atrium. One and 3 stimuli per vagal burst depressed AP up to 62 and 90%, respectively. The response varied with the time in the cardiac cycle at which the stimulus was given. Identical stimuli produced a greater inotropic depression at longer cardiac cycle durations. The differences between the magnitudes of the AP responses at two different mean heart rates were relatively constant when the stimulus intensity was increased from 1 to 99 stimuli per burst. A low-level stimulus caused a greater depression in contractile force when the heart rate was allowed to change than with the identical stimulus when the heart was paced, although this difference in paced- and unpaced-heart responses tended to disappear when the stimulus intensity (burst width) was increased. The composite frequency-force relationship was relatively flat over normal heart periods, but fell off by 15-20% at the extremes. The present results show an unexpected interaction between the vagal inotropic effect and the frequency-force relationship such that a given vagal stimulus causes a greater depression of atrial contractile force at lower heart rates.

Animals↗
PubMed1980

Time-dependent heart period and contractility responses to successive brief vagal stimuli.

The vagosympathetic trunks of anesthetized propranolized dogs were stimulated with brief electrical bursts, and heart period (P-P interval), atrioventricular conduction (P-R interval), and pressure generated on a balloon anchored in the atrium (AP) were measured. Two vagal stimulus bursts were given separated by an integral number of cardiac cycles but with each placed at the same relative time in the cardiac cycle. The time between stimulus bursts (T) varied from 2 to 60 s. For all cardiac variables over this time span, the peak response to the second stimulus (P2) was less than that of the first (P1) i.e., the ratio P2/P1 was less than unity. The maximum depression of P2/P1 for all variables occurred at a T of about 5 s. The effect of changing the time in the cardiac cycle at which the stimulus was given, and the effect of stimulus intensity on the P2/P1 ratio was also measured. Previous experiments observing the P-R interval alone suggested that synthesis and release of acetylcholine were not involved in the time dependent P2/P1 effect. The present results suggest that neuroeffector mechanisms at the target cellular level are also not involved in the depression of P2/P1. A time-dependent increase in acetylcholine inactivation is consistent with the present results, but an antagonism between primary and secondary inhibitory effects also cannot be ruled out.

Animals↗
PubMed1980

The effect of pentoxifylline on red cell deformability in cerebrovascular accidents.

A study was carried out in 49 recent cerebrovascular accident (CVA) patients to compare red cell deformability in this group with that in 65 healthy controls. Deformability was determined using a standard technique for measuring blood filtration time through a micropore filter. Filtration time was shown to be significantly reduced in the CVA patients. All patients had ACTH treatment, 28 of them receiving in addition 600 mg pentoxifylline per day, either by intravenous infusion or by intramuscular injection. After 2-weeks' treatment, red cell deformability was increased in the patients treated with pentoxifylline and ACTH and was unchanged in the 21 patients receiving only ACTH (p less than 0.001). The authors discuss the role of increased red cell deformability in the clinical prognosis of the patients.

Adrenocorticotropic Hormone↗
PubMed1980

Drip infusion cholangiography using iotroxamide. Double blind comparison with ioglycamide.

A double blind clinical trial was carried out in 200 unselected patients to compare the efficacy and tolerance of ioglycamide and iotroxamide as contrast media for intravenous cholangiography. The two agents were administered by slow infusion at a rate of 2.6 mumoles/kg bodyweight/minute for one hour. Radiological opacification of the bile duct was assessed independently by two radiologists. In patients with serum bilirubin levels of less than 34 mumoles/litre visualization of the bile duct was significantly better with iotroxamide than with ioglycamide (P < 0.001). Toxic side effects were observed in 8% of patients receiving ioglycamide and in only 3% of the patients given iotroxamide.

Adult↗
PubMed1980

[Influence of age on the secretion of gastric juice and electrolytes in the preruminant calf].

Four preruminant Friesian calves were fitted with an innervated abomasal fundic pouch cut from the lesser curvature. They were fed twice daily a milk substitute containing only spray-dried skim-milk powder as protein source. The daily outflow of gastric juice regularly increased from 400 to 1 800 g/day between 2 and 16 weeks of age and did not change later. The daily outflow/100 kg liveweight increased until 7 to 9 weeks of age and decreased later until 30 weeks (fig. 1). The pH of the secretion always ranged between 1 and 2, except during the days following surgery and when the calves were ill (fig. 2). Expressed in absolute terms, the total outflow of hydrogen, sodium, potassium and chloride ions increased with age; this was mainly due to the increase in the outflow of gastric juice since the ion concentration showed a cyclic pattern with age (fig. 3). When expressed on a liveweight basis, the daily ion output alternatively showed increasing and decreasing periods, mainly in relation to changes in concentration, but no significant trend with age was observed (fig. 4).

Abomasum↗
PubMed1980

Double minutes in human large bowel cancer.

Two patients with large bowel carcinoma are described in whose tumors the presence of double minutes was observed. In one of these, the first such patient to be reported, double minutes were present in 100% of metaphases examined in both the primary tumor and its liver metastasis. The number of double minutes varied from 6 to 93 per metaphase. In the second patient, double minutes were seen only in two metaphases. The literature on double minutes is summarized, and it is concluded that double minutes are found in a wide spectrum of tumors, including human large bowel cancer and are not confined to tumors of neurogenic origin as suggested by earlier workers. In additon, evidence is suggestive of an association between the lack of differentiation and the presence of double minutes, but further data are required to substantiate this.

Adenocarcinoma↗
PubMed1980

In vivo and in vitro induction of cytochrome P-450 synthesis in hyperoxia.

Exposure of dark- or light-adapted mice to 1--3 ATA oxygen for times ranging from 15 min to 4 h caused a progressive increase in P-450, which peaked and then decayed. The rate of decay appears to be independent of PO2. A linear, inverse relationship was noted between the PO2 in the range of 1--4 ATA and the duration of exposure needed to obtain maximum P-450 levels. Cytochrome P-450 was induced by hyperoxia in vitro in a suspension of hepatocytes, and this induction was prevented by inhibitors of transcription and translation and by disulfiram. Cytochrome P-450 induction is not a general phenomenon of stress, albeit physical restraint may decrease the level of P-450 induced. Induction was a specific effect of increased oxygen tensions and was not due to pressure per se. Neither equivalent pressures of compressed air in the in vivo experiments nor equivalent pressures of nitrogen in the in vitro experiments induced P-450. Induction in vivo was inhibited by disulfiram and metyrapone. Hyperoxia is the most rapid inducer of P-450 yet found, and this response may represent a protective mechanism against hyperoxia.

Animals↗
PubMed1979

Location of the stilbenedisulfonate binding site of the human erythrocyte anion-exchange system by resonance energy transfer.

The stilbenedisulfonate inhibitory site of the human erythrocyte anion-exchange system has been characterized by using serveral fluorescent stilbenedisulfonates. The covalent inhibitor 4-benzamido-4'-isothiocyanostilbene-2,2'-disulfonate (BIDS) reacts specifically with the band 3 protein of the plasma membrane when added to intact erythrocytes, and the reversible inhibitors 4,4'-dibenzamidostilbene-2,2'-disulfonate (DBDS) and 4-benzamido-4'-aminostilbene-2,2'-disulfonate (BADS) show a fluorescence enhancement upon binding to the inhibitory site on erythrocyte ghosts. The fluorescence properties of all three bound probes indicate a rigid, hydrophobic site with nearby tryptophan residues. The Triton X-100 solublized and purified band 3 protein has similar affinities for DBDS, BADS, and 4,4'-dinitrostilbene-2,2'-disulfonate (DNDS) to those observed on intact erythrocytes and erythrocyte ghosts, showing that the anion binding site is not perturbed by the solubilization procedure. The distance between the stilbenedisulfonate binding site and a group of cysteine residues on the 40 000-dalton amino-terminal cytoplasmic domain of band 3 was measured by the fluorescence resonance energy transfer technique. Four different fluorescent sulfhydryl reagents were used as either energy transfer donors or energy transfer acceptors in combination with the stilbenedisulfonates (BIDS, DBDS, BADS, and DNDS). Efficiencies of transfer were measured by sensitized emisssion, donor quenching, and donor lifetime changes. Although these sites are approachable from opposite sides of the membrane by impermeant reagents, they are separated by only 34--42 A, indicating that the anion binding site is located in a protein cleft which extends some distance into the membrane.

Energy Transfer↗
PubMed1979

The use of bone core biopsies for cytogenetic analysis.

Cultures of bone core specimens have proved satisfactory for cytogenetic analysis in patients from whom it was impossible to obtain a bone marrow aspirate, or in whose peripheral blood dividing myeloid cells were absent or insufficient in number. The quality of the metaphase chromosome is adequate for banding studies.

Adult↗
PubMed1979

Chromosome analysis of primary large bowel tumors: a new method for improving the yield of analyzable metaphases.

Colon tumors were processed immediately after surgical resection. Using L-Arterenol and sodium citrate in combination with standard chromosome culture techniques, 12 of 17 consecutive tumors (75%) had countable figures ranging from 5 cells to 59 cells. Seven of the 12 cases had over 25 countable cells. Chromosome counts did not vary more than +/- 4 for any one case. Seven tumors were karyotyped, 6 with banding techniques. One of these specimens had mosaic patterns. The chromosome counts varied: 2 were hypodiploid; 1 was pseudodiploid and 4 were hyperdyploid. There were some similarities in the karotypes although no identical karyotypes were seen in this series.

Adenocarcinoma↗
PubMed1979

Gastric, pancreatic, and biliary secretion and the rate of gastric emptying after parietal cell vagotomy.

We compared the gastric, pancreatic, and biliary secretory responses to a liquid test meal and the rates of gastric emptying of liquid and solid test meals in six patients at least 1 year after parietal cell vagotomy with eight unoperated subjects, one with duodenal ulcer disease and seven normal control subjects. Parietal cell vagotomy decreased gastric acid secretion to one third of normal, but total trypsin and bile salt secretion during the first 150 postcibal minutes were normal. The liquid test meal emptied from the stomach faster after parietal cell vagotomy, the pattern of emptying being exponential in the vagotomy patients and linear in the normal subjects. The rate of gastric emptying of a liquid meal, although faster than normal, was less precipitous after parietal cell vagotomy than after truncal vagotomy plus drainage or subtotal gastrectomy, and trypsin and bile salt concentrations were not diluted to abnormal levels, as occurs after these other procedures. Furthermore, emptying and dispersion of solid food remained normal after parietal cell vagotomy. These findings probably explain, at least in part, the decreased incidence of postprandial dumping and diarrhea that accompanies parietal cell vagotomy compared with the other popular operations for duodenal ulcer.

Adult↗