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Biomedical subjects

M Ichikawa

Publications and source records attributed to M Ichikawa.

At least 325 records · Page 18Linked to original sources
PubMed1986

Studies of nitrogen balance in male highlanders in Papua New Guinea.

Nitrogen metabolism in Papua New Guinea highlanders was studied by examining their nitrogen balance when they ate their usual diet (experiment 1) or an experimental diet (experiment 2). Studies were made on 39 male highlanders between October and December in 1980 and 1982. In experiment 1, the average protein and energy intakes (mean +/- SD) for three consecutive days of usual diets were 116.2 +/- 31.2 mg N/kg body weight and 46.9 +/- 8.9 kcal/kg body weight in 1980 and 143.5 +/- 54.8 mg N/kg body weight and 47.3 +/- 10.5 kcal/kg body weight in 1982, and thus the nitrogen balances were 27.7 +/- 28.3 and 18.4 +/- 24.2 mg N/kg body weight, respectively. Most dietary protein and energy was derived from sweet potatoes and other vegetable foods, but between 1980 and 1982 the diet changed slightly with increased consumption of imported foods such as rice and canned fish. In the second experiment, when 10 highlanders were given adequate protein diet (about 200 mg N/kg body weight and about 44 kcal total energy/kg body weight for 13 d, much of the dietary nitrogen was retained in their bodies (45.1 +/- 19.3 mg N/kg body weight). When another group of men were fed a sweet-potato diet (81.1 mg N/kg body weight for 8 d followed by a low protein sweet-potato diet containing only 42 mg N/kg body weight with 50 kcal/kg body weight for 14 d, nitrogen true digestibility and net protein utilization increased and their nitrogen balance showed no significant change (-11.0 +/- 5.6 mg N/kg body weight).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Hyperactive phagocytosis by circulating neutrophils and monocytes in Chédiak-Higashi syndrome.

Phagocytic capacity of circulating neutrophils and monocytes was studied by electron microscopy in 2 children with Chédiak-Higashi syndrome (CHS). Apparent phagocytosis of autologous leucocytes by the CHS neutrophils and monocytes was demonstrated when they were coincubated with Staphylococcus aureus in vitro, indicating their capacity for hyperactive phagocytosis. The hyperactive phagocytic capacity of the CHS phagocytes was a cellular abnormality. CHS neutrophils and monocytes are known to be defective in chemotaxis and bactericidal capacity, and the hyperactive phagocytic capacity is another functional abnormality of CHS phagocytes.

Blood Cells↗
PubMed1986

Effect of dietary protein levels on urea utilization in Papua New Guinea highlanders.

Ability to utilize urea nitrogen for body protein synthesis was examined with Papua New Guinea (PNG) highlanders and Japanese (JPN). Eight male PNG highlanders and 8 male JPN were fed on a low protein diet containing 0.55 g protein/kg or an adequate protein diet containing 1.34 g protein/kg for 1 or 2 weeks. The fate of 15N was measured after oral administration of 15N-labelled urea. There was no difference in 15N incorporation into serum protein between PNG highlanders and JPN receiving low protein diets. On the other hand, on the adequate protein diet, 15N incorporation in PNG highlanders was similar to that on the low protein diet, in contrast to that in JPN which was hardly detected in the adequate protein diet. When PNG highlanders take more protein than protein in their usual diet, they effectively incorporate ingested protein into their body protein and urea nitrogen is utilized for synthesis of body protein.

Adolescent↗
PubMed1986

Age-related changes in nitrogen balance and related variables in later life of aging male Wistar rats.

Age-related changes in nitrogen balance and related variables in later life of male Wistar rats fed 14.0 g/day (group C) or 8.7 g/day (group R) of 20% casein diet throughout life were examined at intervals of 50 days from day 650 of age. In both groups, body weight decreased from about day 600, and the body weight at the final examinations (on day 1,000 in group C and 1,100 in group R) were 18% and 13%, respectively, less than those on day 600, although the animals consumed more than 98% of their food throughout. Their nitrogen balance fluctuated throughout later life in both groups, but the overall changes did not show a consistent negative or positive pattern. Consequently, the mean nitrogen balance after 650 days of age was calculated as -11.5 +/- 45.3 mg N/day in group C and -1.3 +/- 11.6 mg N/day in group R. On the other hand, protein digestibility increased steadily after 650 days of age in both groups. As a whole, nitrogen metabolism at the whole body level did not change consistently even in later life.

Aging↗
PubMed1986

Dissociation of protective immunity against tuberculosis and tuberculin hypersensitivity at a level of lymphokines.

On the basis of present knowledge on the purification and the action mechanisms of macrophage regulating lymphokines, as summarized in Table VIII, tuberculosis immunity and tuberculin delayed type hypersensitivity may be dissociated at a level of responsible lymphokines. Table VIII. Dissociation of TB-IMM and DTH at a level of lymphokine 1. Purification of mediators resulted in separation of MIF/MAF and MCF 2. Anti-MIF antibody has no suppression of MCF reaction 3. Lipid metabolisms of macrophages stimulated with MIF/MAF and MCF are different 4. MIF/MAF suppresses MCF-reaction through monokines.

Animals↗
PubMed1985

Distribution of corticocortical and thalamocortical synapses on identified motor cortical neurons in the cat: Golgi, electron microscopic and degeneration study.

Details of the terminal connection of corticocortical and thalamocortical fibers on pyramidal and stellate neurons in the cat motor cortex were studied using the electron microscope in combination with the Golgi and axonal degeneration techniques. Corticocortical terminals were examined in 23 identified neurons of which 11 were pyramidal and 12 were stellate. Stellate neurons located in layer III received many degenerating terminals (average 8.4 +/- 2.2 per unit length of dendrite (ULD)) and the majority of these (95%) were found on the proximal dendrites or on the cell bodies. The pyramidal neurons received fewer degenerating terminals (average 2.1 +/- 0.27/ULD) and these were located on more distal dendritic shafts or on dendritic spines. The majority of these synapses were of the asymmetric type. Thalamocortical terminals were examined in 9 pyramidal and 9 stellate neurons. Pyramidal neurons received many terminals (average 6.0 +/- 1.23/ULD) and these were found on the basal as well as the apical dendrites and on dendrite spines. Stellate neurons received fewer terminals (average 4.2 +/- 0.64/ULD) and were located primarily on proximal dendritic shafts. The majority of these synapses were of the asymmetric type. The functional role of these synapses is discussed in relation to the physiological results reported in the preceding paper.

Animals↗
PubMed1985

Functional role of cysteinyl residues in tryptophanase.

Holotryptophanase inactivated by oxidation of cysteinyl residues showed a different absorption spectrum from the native enzyme. At pH 8.0, the native enzyme preferentially existed as a 337-nm species (active form), whereas in the inactive enzyme a 420-nm species (inactive form) was dominant. During the reactivation of the enzyme by reduction with dithiothreitol, an increase at 337 nm and a decrease at 420 nm were observed with concomitant increase in enzymatic activity, which was accompanied by the appearance of two cysteinyl residues per monomer. Specific S-cyanylation of cysteinyl residues by nitrothiocyanobenzoic-acid-inactivated apotryptophanase with the modification of one cysteinyl residue per monomer, whereas holotryptophanase was highly resistant to inactivation with nitrothiocyanobenzoic acid. The essential role of the active-site-bound pyridoxal 5'-phosphate in protection against inactivation was confirmed by the agreement of the K1/2 (protection) of 5.0 microM for pyridoxal 5'-phosphate with Km of 2.0 microM in enzyme catalysis. The inactivation by nitrothiocyanobenzoic acid caused a similar shift in the equilibrium between the 337-nm species and 420-nm species, i.e. decrease of the 337-nm species and increase of the 420-nm species. From the pH dependence of the equilibrium between these two species, pKa of 7.9 and 7.4 was obtained for the inactive and the dithiothreitol-activated enzyme, respectively, indicating that cysteinyl residue(s) participated in lowering the pKa of the interconversion between the 337-nm species (active form) and 420-nm species (inactive form). The possible role of cysteinyl residues in the function of tryptophanase is discussed.

Catalysis↗
PubMed1985

Modified Hodgkin-Huxley gating kinetics of sodium activation in giant axons of squid (Doryteuthis bleekeri).

The probabilities m of the sodium activation gate being open are shown to fit experimentally-determined running integrals Qg of recordings of the colchicine-sensitive fraction of the asymmetry current, within the Hodgkin-Huxley framework that the gate could have only two conformations, open and closed. Using the Hodgkin-Huxley framework, we are obliged to assume that the transition velocities, alpha m and beta m, between the open and closed gates depend not only on membrane potentials V but also on the time after a potential step was externally applied. We introduce the following functions of alpha m and beta m. (sequence in text) where VH, td and tau p stand for holding potential, constant delay time of 10 microseconds, and transit time of the transition velocity of alpha m (or beta m) from its initial value alpha om (or beta om) to its final steady value alpha infinity m (or beta infinity m), respectively. The transit time tau p was found to be potential-dependent; typically it was 30 microseconds at -20 mV, and 100 microseconds at 20-40 mV. The values of alpha infinity m, alpha om, beta infinity m and beta om were found to be in reasonable agreement with those obtained by others, under the Hodgkin-Huxley assumption that the gate followed first-order kinetics. The requirement of new parameters, tau p and td, in the transition velocities was discussed in a relation to a membrane model where a voltage-receptor and a sodium channel macromolecule are spatially separated but functionally connected through underlying cytoskeletons (Matsumoto, 1984).

Animals↗
PubMed1985

Kinetics of sodium activation in giant axons of squid (Doryteuthis bleekeri).

The variation with time of the rising phase of the sodium conductance in squid giant axons was fitted to the Xth power of running integrals of the colchicine-sensitive components of the asymmetry currents, where the running integrals were experimentally obtained. We found that excellent fitting was obtained for all of the potentials examined from -60 to +60 mV, when we put the value of X equal to 3 at potentials above 10 mV and equal to 5 below -20 mV, and it varied continuously from 3 to 5 when pulse potentials changed from 10 to -25 mV. Further, it was found that the voltage dependence of the peak sodium currents was fitted to the third power of charges carried by the colchicine-sensitive component of the asymmetry current by the moment when the sodium current attained its peak. These results agree well with the expectation by Hodgkin and Huxley [(1952) J. Physiol., Lond. 117, 500-544] although the gating kinetics differ from the Hodgkin-Huxley prediction [Matsumoto, Ichikawa and Tasaki (1983) J. Membr. Biol. 77, 93-99].

Animals↗
PubMed1985

Blood status and serum free amino acids in Papua New Guinea highlanders.

Hematological values and serum amino-acid concentrations were measured in 17 healthy male adult Papua New Guinea highlanders who live on a sweet-potato staple diet. Hematological values were within the normal range, except for a low serum urea concentration. The concentrations of serum threonine, valine, isoleucine, leucine and tyrosine were significantly lower, and those of arginine, glutamate, glycine and alanine were significantly higher, than in Japanese controls. These amino acid patterns in the serum of Papua New Guinea highlanders are an indication of low protein nutrition and adequate energy supply. Some essential amino acid and urea concentrations in the serum of nine Papua New Guinea subjects fed on an adequate protein diet (1.3 g/kg body weight, about twice their habitual diet) for 13 days were significantly increased but were still significantly lower than those of Japanese subjects. Serum alanine decreased on an adequate protein diet. These results show that amino acid uptake and utilization by peripheral tissues may be accelerated on an adequate protein diet. Blood status and serum amino acid concentrations did not show any change except for urea and some amino acids, when five Papua New Guinea highlanders were fed on a low protein diet (0.6 g/kg) consecutively for 13 days.

Adolescent↗