Enzymic properties of intestinal aminopeptidase P: a new continuous assay

A continuous photometric assay of aminopeptidase P activity was developed which is based on a coupled enzymic assay with the substrate Gly-Pro-Pro-pNA and DPP IV as auxiliary enzyme. This assay was used to evaluate the kinetic parameters and inhibitory profile of intestinal brush border aminopeptidase P.

[Experiments on the induction of embryopathies and changes in alpha-foetoprotein and serum albumin concentrations in the chick embryo]

Administration of 3 microg dexamethasone at day 8 of incubation into the allantoic cavity resulted in various embryopathies in embryos by the 15th day of incubation. Chicken alpha-foetoprotein (chAFP) and serum albumin concentrations, when examined at the 12th day of incubation, were below the corresponding controls (P<0.01), whereas total serum protein was only slightly lower, On day 15 chAFP concentrations were similar to those of the controls, serum albumin values were markedly reduced and total serum protein was significantly decreased. The results suggested a selective reduction of serum albumin synthesis in the 15-day-old chick embryo. Following administration of 2 IU insulin on the first day of incubation, into the yolk sac, one third of the embryos developed embryopathies. ChAFP, serum albumin and whole serum protein values were unchanged on either the 12th day or 15th day of incubation. Inoculation of 100 microg adrenaline into the allantoic cavity on the sixth day of incubation resulted in embryopathies in only a few instances. ChAFP total serum protein values were not affected. However, serum albumin concentrations were significantly lower on the 12th day, but not on the 15th. The responses to L-thyroxine were both time- and dose-dependent. Inoculation of 2 microg thyroxine on the second day of incubation resulted in few embryopathies. ChAFP levels were significantly lower on the 12th and 15th day of incubation. In contrast, serum albumin and total serum protein concentrations were normal at both times. Similar results were obtained when 2 microg of thyroxine were administered at the third day of incubation. Thus in order to inhibit selectively chAFP synthesis, administration of 2 microg thyroxine on day 2 or 3 of incubation is suggested. When 10 microg thyroxine were injected on day 8 of incubation, 80% of the embryos showed embryopathies on day 12 of incubation. ChAFP and serum albumin levels were markedly depressed. The concentration of total serum protein was significantly decreased on day 12 but less so, though still significantly, on day 15. These results demonstrate the possibility to influence selectively chAFP and serum albumin synthesis, thereby facilitating studies on chemically induced teratological, including pathophysiological, processes in the avian embryo.

P300 and anticipated task difficulty

Recently, it has been shown that P300 measures depend on stimulus evaluation processes. This paper explores the effect of messages informing about the degree of difficulty of subsequent tasks on the P300 component. Ten healthy volunteers were asked to solve mental arithmetic tasks of graduated difficulty. The degree of difficulty was announced by messages which preceded the tasks and which were used as P300 eliciting stimuli. Measurements of the amplitude and latency of P300 components from 3 brain regions (Fz, Cz, Pz) were collected selectively for each category of task difficulty announced. Subjective ratings of difficulty and the frequency of errors confirmed the monotonic increase of task difficulty from categories I to VI. The mean P300 amplitude in categories I-VI showed a U-shaped trend, i.e. the highest amplitude occurred in the extreme categories 'extremely easy' and 'very difficult'. No significant effect of stimulus categories on P300 peak latencies was found. It is concluded that the P300 amplitude reflects an evaluation in the sense of distance judgements on an internal scale which in this study concerned the task difficulty.

An enzymatic method for calibration of serum lipase assays

An enzymatic method for the calibration of a turbidimetric lipase assay is described, based on measurement of free fatty acids liberated by the action of lipase. The substrate of the turbidimetric assay is a colipase-containing triolein emulsion. For determination of the free fatty acids a commercial test kit including acyl-CoA synthetase, acyl-CoA oxidase, and peroxidase is used. Intra- and interassay imprecision (CV) is about 5% at above-normal lipase activities, about 10% at normal values. Temperature coefficients are 1.24 and 1.45, respectively, for measurements at 30 and 37 degrees C vs 25 degrees C.

An enzymatic method for calibration of serum lipase assays

An enzymatic method for the calibration of a turbidimetric lipase assay is described, based on measurement of free fatty acids liberated by the action of lipase. The substrate of the turbidimetric assay is a colipase-containing triolein emulsion. For determination of the free fatty acids a commercial test kit including acyl-CoA synthetase, acyl-CoA oxidase, and peroxidase is used. Intra- and interassay imprecision (CV) is about 5% at above-normal lipase activities, about 10% at normal values. Temperature coefficients are 1.24 and 1.45, respectively, for measurements at 30 and 37 degrees C vs 25 degrees C.

Optimized conditions for determining activity concentration of alpha-amylase in serum, with 1,4-alpha-D-4-nitrophenylmaltoheptaoside as substrate

We describe a method for measuring the catalytic activity of alpha-amylase (EC 3.2.1.1) in serum and urine, by use of a defined substrate: 1,4-alpha, D-4-nitrophenyl maltoheptaoside. We use a phosphate buffer of pH 7.10, containing chloride as activator and alpha-glucosidase (EC 3.2.1.20) as the auxiliary enzyme. After a lag phase of 4 min at 25 degrees C or 30 degrees C, or 3 min at 37 degrees C, the increase of absorption of 4-nitrophenol is measured at 410 nm or 405 nm. The pH value of the assay mixture is a compromise between optimum pH for the alpha-amylase reaction, shortest possible lag phase, and an acceptable absorptivity of 4-nitrophenol. Because the dissociation of 4-nitrophenol depends strongly on pH and temperature, we determined its absorptivity with various combinations of these variables in the assay. Heparin-treated plasma can be used, but not EDTA, fluoride, or citrate. Lipemia, hemoglobin less than or equal to mumol/L, bilirubin less than or equal to 170 mumol/L, glucose less than or equal to 100 mmol/L, and ascorbic acid less than or equal to 1 mmol/L of sample do not interfere in the assay.

Optimized conditions for determining activity concentration of alpha-amylase in serum, with 1,4-alpha-D-4-nitrophenylmaltoheptaoside as substrate

We describe a method for measuring the catalytic activity of alpha-amylase (EC 3.2.1.1) in serum and urine, by use of a defined substrate: 1,4-alpha, D-4-nitrophenyl maltoheptaoside. We use a phosphate buffer of pH 7.10, containing chloride as activator and alpha-glucosidase (EC 3.2.1.20) as the auxiliary enzyme. After a lag phase of 4 min at 25 degrees C or 30 degrees C, or 3 min at 37 degrees C, the increase of absorption of 4-nitrophenol is measured at 410 nm or 405 nm. The pH value of the assay mixture is a compromise between optimum pH for the alpha-amylase reaction, shortest possible lag phase, and an acceptable absorptivity of 4-nitrophenol. Because the dissociation of 4-nitrophenol depends strongly on pH and temperature, we determined its absorptivity with various combinations of these variables in the assay. Heparin-treated plasma can be used, but not EDTA, fluoride, or citrate. Lipemia, hemoglobin less than or equal to mumol/L, bilirubin less than or equal to 170 mumol/L, glucose less than or equal to 100 mmol/L, and ascorbic acid less than or equal to 1 mmol/L of sample do not interfere in the assay.

The distribution of chymotrypsin within the feces and description of a new device for the preparation of stool samples

We measured the distribution of chymotrypsin within feces by comparing duplicate 100-mg stool aliquots from 48 stool specimens. For practical purposes, the distribution of the enzyme in stool appears sufficiently homogeneous to assure representative results even from 100-mg stool aliquots. Given this likelihood, we have developed a new disposable device that measures 100-mg stool aliquots hygienically, prepares this material for shipping by mail, homogenizes and suspends the stool sample, and facilitates centrifugation of the fecal suspension, all within the same instrument. Performance studies with this new device revealed that stools of different consistency can be measured out precisely and conveniently by volume. The difference in the specific weight of different stools appears to be so low that for practical purposes a 100-mg mass of stool can be weighed out by volume.

The distribution of chymotrypsin within the feces and description of a new device for the preparation of stool samples

We measured the distribution of chymotrypsin within feces by comparing duplicate 100-mg stool aliquots from 48 stool specimens. For practical purposes, the distribution of the enzyme in stool appears sufficiently homogeneous to assure representative results even from 100-mg stool aliquots. Given this likelihood, we have developed a new disposable device that measures 100-mg stool aliquots hygienically, prepares this material for shipping by mail, homogenizes and suspends the stool sample, and facilitates centrifugation of the fecal suspension, all within the same instrument. Performance studies with this new device revealed that stools of different consistency can be measured out precisely and conveniently by volume. The difference in the specific weight of different stools appears to be so low that for practical purposes a 100-mg mass of stool can be weighed out by volume.

[Characteristics of preoperative diagnosis in surgery of the aged]

The individual and special risk factors in age patients must take into consideration in indication for operation. The preoperative diagnostic specialty concerned particularity function disturbances of the cardiovascular, bronchopulmonary and gastrointestinal system. Recognition and treatment are described.

Studies on lectin affinities of chicken alpha-fetoprotein during ontogeny

Alpha-fetoprotein in the sera of chicken embryos (ch-AFP) of the 7th, 10th, 13th, 16th, and 19th day of incubation and of one-day-old chickens were examined in crossed-immunoaffino-electrophoresis (CIAE) using different lectins [concanavalin A (Con A), lentil, wheat germ lectin, and soybean lectin] as ligands. Differences in lectin affinities, suggesting different degrees or forms of glycosylation of ch-AFP during ontogeny, were demonstrated by this method. Sera of chicken embryos of the same stages were also subjected to Con A affinity chromatography and the elution patterns were evaluated qualitatively in CIAE and quantitatively in rocket immunoelectrophoresis. These experiments revealed a major Con A-nonreactive and a minor Con A-reactive fraction at the 7th day of incubation. In contrast, a minor Con A nonreactive fraction and a major Con A-reactive fraction were observed at later stages of embryonic life. Extracts from embryos of the 8th and 15th day of incubation did not exhibit heterogeneity when subjected to CIAE. The biological significance of these observations, as well as the biological role of AFP in general, remains to be elucidated. Examination of ch-AFP glycosylation patterns might be included into the spectrum of analyses when certain early teratological processes in the chicken embryo are to be monitored. In addition, these molecular changes have to be considered when in vitro or in vivo experiments on the biological, especially immunological, role of ch-AFP are envisaged.

Inhibition of in vitro lymphocyte blastogenesis by chicken alpha-fetoprotein

Chicken alpha-fetoprotein (ch-AFP), purified from fetal chicken serum and embryo extracts, respectively, was examined for its immunomodulatory effect in vitro. Significant (P less than 0.05) suppression of the allogeneic mixed lymphocyte reaction (MLR) was observed, when these preparations were added to one-way mixed lymphocyte cultures (MLC) in quantities of 62.5-1000 micrograms/ml. Suppression of the MLR was depending on the presence of ch-AFP for at least 16 h after initiation of the MLC, suggesting that this fetal protein was acting mainly in the early phase of lymphoblastogenesis. Serum of chicken embryos (12th and 15th day of incubation), day-old chickens, and of 10-week-old chickens of four different inbred lines were also found to exert suppression of the MLR. From these data, it is hypothesized that ch-AFP plays an immunoregulatory role by maintaining a certain stage of self tolerance during differentiation of the avian immune system.

Lack of immunostimulatory effect of N-acetyl muramyl-L-alanyl-D-isoglutamine on selected chicken immune functions

Synthetic N-acetyl muramyl-L-alanyl-D-isoglutamine, syn. muramyl-dipeptide (MDP) was found to be immunostimulatory in several experimental animal species. In order to determine the influence of MDP on the chicken immune response, different doses (0.05-0.2 mg) of this compound were administered to 6-week old chickens, and cellular as well as humoral immune functions were tested. Neither the immune response against sheep red blood cells or Newcastle disease virus (strain Hitchner B 1), nor the ability to reject skin grafts, or to react in the delayed hypersensitivity (tuberculin) test, were affected significantly under the experimental conditions employed. This study reveals little evidence for parallels between the ability of the chicken immune system and the immune system of other animal species examined so far, to develop enhanced immune reactions under the influence of MDP.