Tooth discoloration by blood: an in vitro histochemical study

Abstract An in vitro model, using a modification of a technique devised by Freccia & Peters, was developed to investigate tooth staining following pulpal haemorrhage. Samples of whole blood, erythrocytes, plasma and platelet concentrate and saline were individually placed in the pulp chambers of groups of five teeth and centrifuged twice daily for 25 min over a period of 3 consecutive days. This confirmed that the blood pigment responsible for the staining was found only in those samples containing erythrocytes. Teeth stained with packed red cells were then prepared for histological examination and subjected to four histochemical tests: (1) benzidine, (2) zinc leuco, (3) Perl's and (4) Turnbull Blue to analyse some of the biochemical changes following haemorrhage into the pulp chamber. These tests showed that, following haemolysis of erythrocytes within dentine, haemoglobin was found either intact or as one of the haematin molecules with no further breakdown of the haem structure and no evidence of any free ferric ions or haemosiderin.     

Effects of meal frequency on body composition during weight control in boxers

The effects of meal frequency on changes in body composition by food restriction were investigated. Twelve boxers were divided between a two meals day⁻¹ group (the 2M group) and a six meals day⁻¹ group (the 6M group). Both groups ingested 5.02 MJ (1200 kcal) day⁻¹ for 2 weeks. Although there was no difference in change of body weight by food restriction between the two groups, the decrease in lean body mass (LBM) was significantly greater in the 2M group than in the 6M group. The decrease in urinary 3-methylhistidine/creatinine was significantly greater in the 6M group than in the 2M group. These results suggest that the lower frequency of meal intake leads to a greater myoprotein catabolism even if the same diet is consumed.     

Catabolite modification of acid tolerance of Streptococcus mutans GS-5

The acid tolerance of Streptococcus mutans GS-5 in standard pH-drop assays was found to be affected by the sugar used in the assay and also by the sugar used for growth of the organism. For example, acid tolerance was lower when galactose was used as catabolite than when glucose was used, apparently because galactose/proton symport brought protons extruded by the F-ATPase back into the cell and thus reduced pH across the cell membrane. The acid tolerance of glycolysis was related directly to the capacities of the cells to produce acid glycolytically, or probably more correctly, to their capacities to produce adenosine triphosphate but not to acid tolerance of phosphotransferase systems for sugar uptake. Thus, glycolytic acid tolerance of S. mutans depends not only on environmental factors such as potassium or magnesium levels but also on the specific catabolites the organism is metabolizing or to which it has become metabolically adapted.     

15N AND PROTEIN METABOLISM

Attempts have been made to estimate the rates of protein synthesis and catabolism in various tissues of rats given different diets adequate or limited in energy and protein using ¹⁵N-labeled glycine. Preliminary data have been obtained with human subjects although the reliability of the estimated rates is as yet uncertain.     

Urinary 3-methylhistidine as an index of dietary protein adequacy in the adult rat: Short term testing

Urinary excretion of 3-methylhistidine (3-MH) was evaluated as an indicator of dietary protein quality using adult rats with shortterm feeding. The effect of protein depletion and repletion on excretion of 3-MH was also studied. Four groups of 6 rats weighing between 250 and 300 grams were fed diets containing 10% protein from casein, wheat gluten, blood globin, or a complementary mixture of wheat gluten and globin. Daily variations of weight, 3-MH and creatinine, as well as 6-day means were observed. The correlation of PER with the 6-day means of urinary 3-MH was not high. Body weight changes and fractional rates of synthesis (based on estimated myofibrillar 3-MH pool size) appeared to be highly correlated to PER and sensitive to the influence of dietary protein and calorie deficiencies on body protein metabolism. 3-MH excretion, then, when used to determine fractional rates of catabolism and synthesis of myofibrillar protein, could be useful in short-term protein evaluation using adult rats.     

Passage of radio-iodinated insulin through the intestinal wall of the rat

Summary ¹³¹I-insulin was given intravenously to normal rats, and the passage of radioactivity into the duodenal loop containing a proteasis inhibitor was studied by two techniques. In the first, the ¹³¹I-insulin was separated from the intestinal content by electrophoresis; whereas in the second, the radioactivity that remained on an ion-exchange resin, directly introduced into the small intestine, was measured. It was found that within 15 minutes from the injection a small amount of ¹³¹I-insulin passes into the gut lumen. — The absorption of ¹³¹I-insulin from small intestine into the blood was studied after introduction of ¹³¹I-insulin along with a proteasis inhibitor into the intestinal loop. The autoradiograph of the electrophoresis of serum showed plasma-protein-bound radioactivity but no radioactivity due to unbound (free) insulin-¹³¹I. — These findings show that the passage of insulin through the intestinal wall of rats can be demonstrated by neutralizing the proteolytic activity in the intestinal tract. The possible role of this passage in protein-losing enteropathy is pointed out.

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Passage von radiojodmarkiertem, Insulin durch die Darmwand der Ratte

Zusammenfassung Normale Ratten erhielten ¹³¹I-Insulin i.V., und der Übertritt der Radioaktivität in das Lumen des Zwölffingerdarms, das einen Proteasen-Inhibitor (Trasylol) enthielt, wurde mittelszweier Verfahren untersucht. Bei dem ersten wurde das ¹³¹I-Insulin durch Elektrophorese vom Darminhalt getrennt, während beim zweiten ein Ionenaustauscher direkt in den Darm eingeführt und dann die daran haftende Radioaktivität gemessen wurde. Dabei fand sich, daß 15 Minuten nach der Injektion eine kleine Menge ¹³¹I-Insulin in das Darmlumen übertritt. — Die Absorption von ¹³¹I-Insulin aus dem Dünndarm in das Blut wurde nach Einbringen von ¹³¹I-Insulin zusammen mit einem Proteasen-Hemmer in die Darmschleife untersucht. Die Autoradiographie der Serumelektrophorese zeigte an Plasmaeiweiß gebundene Radioaktivität, jedoch kein nichtgebundenes (freies) ¹³¹I-Insulin. — Aus diesen Untersuchungen geht hervor, daß sich der Durchtritt von Insulin durch die Darmwand bei Ratten nach Neutralisierung der proteolytischen Aktivität im Verdauungstrakt nachweisen läßt. Es wird auf die mögliche Bedeutung dieser Passage bei Enteropathien mit Eiweißverlust hingewiesen.

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Passage d'insuline marquée à l'iode radioactif à travers la paroi intestinale du rat

Résumé Des rats normaux ont reçu de l'insuline-¹³¹I par voie intraveineuse et le passage de la radioactivité à l'intérieur du duodénum, contenant un inhibiteur de la protéolyse (Trasylol), a été déterminé par deux méthodes. Pour la première, l'insuline-¹³¹I a été séparée du contenu intestinal par électrophorèse, tandis que pour la deuxième, nous avons mesuré la radioactivité fixée sur résine échangeuse d'ions introduite directement dans l'intestin. Nous avons trouvé que 15 minutes après l'injection une petite quantité d'insuline passe dans la lumière intestinale. — L'absorption d'insuline-¹³¹I de l'intestin grêle vers le sang a été déterminée après introduction combinée d'insuline-¹³¹I avec un inhibiteur de la protéolyse dans une anse intestinale. L'autoradiographie de l'électrophorèse du sérum a montré une radioactivité liée aux protéines du plasma, mais pas d'insuline-¹³¹I non-liée (libre). — Ces recherches montrent que le passage d'insuline à travers la paroi intestinale du rat peut être démontré après neutralisation de l'activité protéolytique dans l'intestin. Un rôle possible de ce passage dans les entéropathies avec perte de protéines est suggéré.

     

Evidence for the control of a mutation in lysine catabolism by the mating type in Yarrowia lipolytica

Summary Reversions of a mutation lye 1.5 blocking the first step of the lysine catabolic pathway were isolated. These reversions mapped inside the LYC1 locus. They exhibited an alteration of the regulation of the lysine pool after nitrogen and phosphorus starvation. This phenomenon did not appear in sexual diploids homozygous for the reversion. Diploids homozygous for the mating type were constructed by protoplast fusion. They displayed a pattern similar to that of the haploids. We conclude that the expression of this mutation is under the control of the physiological state of the mating type.Preliminary accounts were presented at the We International Congress of Genetics (New Delhi, December 1983)     

Genetic variation in sialidase and linkage to N-acetylneuraminate catabolism in Mycoplasma synoviae

We explored the genetic basis for intraspecific variation in mycoplasmal sialidase activity that correlates with virulence, and its potentially advantageous linkage to nutrient catabolism. Polymorphism in N-acetylneuraminate scavenging and degradation genes (sialidase, N-acetylneuraminate lyase, N-acetylmannosamine kinase, N-acetylmannosamine-6-phosphate epimerase, N-acetylglucosamine-6-phosphate deacetylase, and glucosamine-6-phosphate deaminase) was evident among eight strains of the avian pathogen Mycoplasma synoviae. Most differences were single nucleotide polymorphisms, ranging from 0.34+/-0.04 substitutions per 100 bp for N-acetylmannosamine kinase to 0.65+/-0.03 for the single-copy sialidase gene nanI. Missense mutations were twice as common as silent mutations in nanI; 26% resulted in amino acids dissimilar to consensus; and there was a 12-base deletion near the nanI promoter in strain WVU1853(T), supporting a complex genetic basis for differences in sialidase activity. Two strains had identical frameshifts in the N-acetylneuraminate lyase gene nanA, resulting in nonsense mutations, and both had downstream deletions in nanA. Such genetic lesions uncouple extracellular liberation of sialic acid from generation of fructose-6-phosphate and pyruvate via intracellular N-acetylneuraminate degradation. Retention of nanI by such strains, but not others in the M. synoviae phylogenetic cluster, is evidence that sialidase has an important non-nutritional role in the ecology of M. synoviae and certain other mycoplasmas.