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Biomedical subjects

I Kleinberg

Publications and source records attributed to I Kleinberg.

At least 55 records · Page 3Linked to original sources
PubMed1983

The free amino acids in human dental plaque.

Analysis of plaques from maxillary and mandibular incisors for free amino acids showed that the dicarboxylic amino acids, glutamic and aspartic, were present in largest amounts, with glutamic acid comprising at least 50 per cent of the total pool. Other amino acids in decreasing order of prominence included proline, ornithine, alanine, lysine, glycine, threonine and serine. This pattern was basically the same in the plaques from the different incisor sites but was clearly different from those of hydrolysates of either the plaque bacteria or the plaque matrix. The results were consistent with the most prominent plaque-free amino acids being associated mainly with the intermediary metabolism of the plaque bacteria. Urea and glucose were then applied to plaque in vivo in the form of rinses to determine if during their metabolism any of the plaque amino acids are affected. Glutamic- and aspartic-acid concentrations both rose after plaque exposure to urea accompanied by a small rise in alanine. After glucose exposure, aspartic- and glutamic-acid concentrations both showed large decreases and alanine showed a small increase. With glucose plus urea, glutamic acid rose and fell, aspartic acid decreased slightly and alanine increased several fold. In each case, the other free amino acids showed little or no change. Thus glutamic and aspartic acids are major components of the intra-cellular pool of amino acids and probably play an important role in alanine synthesis, presumably by facilitating transamination of pyruvate.

Adult↗
PubMed1983

Catabolism of arginine by the mixed bacteria in human salivary sediment under conditions of low and high glucose concentration.

The catabolism of glucose by the oral mixed bacteria results in a lowering of the pH whereas arginine degradation favours a rise. In the mouth, low and high levels of glucose cause different plaque pH conditions which, in turn, might affect the rate and mode of degradation of arginine. This possibility was examined in the suspended salivary-sediment system where these pH conditions can be simulated. With the pH, the metabolic parameters examined were arginine utilization, ammonia, carbon dioxide and putrescine formation, utilization of glucose and changes in levels of L(+)- and D(-)-lactic acid. At the lower glucose concentration, the pH rapidly fell and then slowly rose whereas, with the higher glucose level, the pH showed a greater fall and no subsequent rise. The more acidic pH conditions favoured by the higher glucose level inhibited arginine degradation and the appearance of its various end-products and intermediates. Arginine degradation with arginine-[U-14C] and paper chromatography-autoradiography showed successive appearance of citrulline, ornithine and putrescine and, depending upon the pH, some succinate. When the pH was held constant at several different values, arginine degradation was optimal when the pH was near neutrality. In supplementary experiments, arginine had little effect on the ability of the oral mixed bacteria to utilize glucose and produce and utilize lactic acid, whereas the arginine peptide, arginylisoleucine and saliva supernatant stimulated these processes. Thus glycolysis enhancement and a more rapid clearance of fermentable carbohydrate by the oral bacteria would accompany pH-rise activity with arginine peptide and saliva but would not accompany pH-rise activity with arginine.

Ammonia↗
PubMed1983

Quantitative assessment of urea, glucose and ammonia changes in human dental plaque and saliva following rinsing with urea and glucose.

The rates of three processes associated with the rise and fall in plaque pH, that normally occur following a urea rinse, were determined: (i) disappearance of urea from plaque, (ii) disappearance of urea from saliva and (iii) formation and disappearance from plaque of the ammonia produced by the plaque bacteria from the urea. Also examined were two processes associated with the fall and rise in pH following a glucose rinse: the disappearance of glucose from plaque and from saliva. Entry into plaque of either urea or glucose during rinsing was immediate; the subsequent disappearance of both from the plaque was slow and followed first-order kinetics. The ammonia formation and urea-disappearance results suggested that clearance of urea from the plaque occurred mainly by bacterial degradation and not by diffusion out of the plaque. The rate constants for ammonia formation and for its subsequent disappearance from the plaque made it clear why a rapid rise and a slow subsequent fall in the pH occurs after urea rinsing. The rate constants enabled calculation of the ammonia produced as a percentage of the urea utilized. Only 16-26 per cent of the urea was recovered as ammonia and the remainder of the urea-N was stored probably as NH2 moieties of certain amino acids. Such storage may enable the plaque bacteria to maintain the pH at an elevated level for an extended period of time by bacterial production of ammonia from these stored compounds after the urea ceases to be available as a source of substrate.

Ammonia↗
PubMed1979

Studies on the incongruent solubility of hydroxyapatite.

The solubility of hydroxyapatite was examined in calcium phosphate mixtures produced by combining Ca(OH)2 and H3PO4 in varying proportions under a wide variety of conditions. Analyses of supernatants for calcium, phosphorus, and pH provided the data for solubility calculations. Alteration of the solid/liquid ratio by removing supernatant or by evacuating water from equilibrated mixtures had little effect on the solubility product. However, when precipitates separated from some mixtures were reequilibrated at various solid/solution ratios in either water, acetate buffer, or supernatants obtained from previous equilibrations, incongruent solubility was demonstrated and was attributed to the formation of other calcium phosphate phases which coated the apatite. The experiments indicated that hydroxyapatite has a thermodynamic solubility product between 10(-57) and 10(-60), but the exact value is difficult to determine because of the formation of surface coats.

Calcium Phosphates↗
PubMed1979

Modification of intramuscular pH oscillations in the isolated perfused rat heart by different interventions.

Changes in the intramuscular pH oscillations were examined by the use of an antimony electrode upon perfusing the isolated rat heart under different experimental conditions. The pH oscillations were decreased upon perfusing the hearts with Na+- or Ca2+-free medium and increased upon perfusing with K+-free medium. Increasing the temperature of perfusion medium from 25 to 40 degrees C or omitting glucose from the perfusing medium decreased the magnitude of oscillations. On the other hand, complete interruption of the perfusion flow resulted in an increase in the amplitude of pH oscillation. An initial increase followed by a decrease in the pH oscillation was seen when hearts were perfused with medium containing lactic acid at pH 6.6. These results suggest that pH oscillations reflect fluctuations in myocardial metabolism.

Animals↗
PubMed1977

An X-ray crystallographic examination of calcium phosphate formation in Ca(OH)2/H3PO4 mixtures.

Precipitates formed over a 10 day period by adding variable amounts of Ca(OH)2 to H3PO4 were examined chemically and by X-ray diffraction in order to determine and to relate the crystallographic changes observed during calcium phosphate formation in this system to those seen previously in dental plaque. In the lower Ca(OH)2/H3PO4 ratio mixtures the initial precipitates were amorphous or poorly crystalline. The latter deposits showed an apatite-like diffraction pattern which changed to brushite and decreased in Ca/P ratio from approximately 1.2-1.0. Since the amorphous precipitates showed a similar decrease in the Ca/P ratio and a transient appearance of apatite, it was suggested that these initial precipitates, like the poorly crystalline deposits, may contain brushite amorphous to X-rays. Precipitates from the higher Ca(OH)2/H3PO4 ratio mixtures changed from a poorly crystalline to a more crystalline apatite and the Ca/P ratio remained fairly constant. The relation between the pH, Ca and P on the one hand and the brushite and apatite contents and the pattern of crystallization of the precipitates on the other was strikingly similar to the same realtionship observed earlier in dental plaque in situ, suggesting that the system used in this study could be used to study certain aspects of plaque mineralization in vitro.

Apatites↗
PubMed1976

Gingival crevicular fluid: a new diagnostic aid in managing the periodontal patient.

On the whole, the studies on GCF have demonstrated that the flow of this fluid is sufficiently indicative of the inflammatory state that it can be used under a variety of clinical conditions to monitor and control gingival inflammation. Since gingivitis is extremely common, and since some cases of gingivitis presumably do not progress to periodontitis, the question could be posed whether or not a concerted effort to control inflammation (i.e. trying to achieve a GCF flow as near to zero as possible) would be clinically significant. Until there is evidence to the contrary, the answer must be "yes", since few cases are known where periodontitis occurs without being preceded by gingivitis. In other words, the control of all gingivitis, if feasible, should prevent most cases of periodontitis. Although control of all gingivitis would mean the treatment of many cases that would not progress to periodontal breakdown, such efforts would be worth-while if most periodontal destruction were prevented. Even the early destructive lesion exhibiting little or no inflammation may soon be identified, mainly because the minute volume of fluid collected from the gingival crevice can now be measured accurately. Accordingly, the concentration of various constituents in the GCF can be determined, which should lead to the development of tests to differentiate between pockets undergoing active destruction with minimal inflammation from the majority of active lesions that are intimately involved with frank inflammation. Thus, a clinician would measure sub-clinical gingival inflammation by measuring GCF flow, then differentiate destructive from quiescent lesions by analyzing the GCF sample for some constituent(s), chemical or microbial (Listgarten et al. 1975) indicative of the periodontal destructive process. Monitoring the flow of GCF might be of value in other clinical situations. For example, one could monitor the response of gingival tissues to various restorative and prosthetic procedures (Strauss et al. 1975) to ensure that these procedures do not aggravate the periodontal tissues and induce gingivitis or periodontitis. The education of the patient should be easier since patients can read their own numbers on the GCF meter at each examination and self-evaluate their personal periodontal condition and the effectiveness of their home care. Even the education of the dental student should be easier since he or she would have the means of self-evaluating the effectiveness of treatment, and not be as dependent upon the subjective assessment of his efforts by an instructor. Finally, monitoring GCF for various components could provide the dentist with a valuable means of easily screening patients for systemic disease. Obviously, this area of investigation is in its infancy, but does promise an exciting future for the oral diagnostician.

Ammonia↗
PubMed1975

Mercury vapor as an atmospheric contaminant of dental offices.

Airborne mercury from dental offices was selectively trapped by silber gauze elements in borosilicate glass obsorbers, followed by heat-desorption and spectrophotometric measurement at 2537A. As little as 0.4 ng of Hg could be accurately determined, which is equivalent to 49 ppt in a wone-L air sample on a v/v basis. Over 860 air samples were taken over a range of locations and working conditions at 88 different dental offices, and at the Dental Training Clinic of the University of Manitoba. The Hg vapor concentrations at the dental facilities ranged from 0.45 to 742 mug/m3 of air, 29% of the samples were within 0.45 to 5 mug; 37.8 were within 5.1 to 25mug;and 33.2% were above 25 mug. Mercury concentrations varied during the working day, depending on the time of sampling, the number of amalgams placed, and the interval between placements. The lowest concentrations were obtained in the morning. Disturbance of residual mercury droplets on floors or working areas by sweeping or dusting, or immediately after attempted clean-up of a mercury spill, sharply increased the amount of airborne mercury.

Air Pollutants↗