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Biomedical subjects

T Oka

Publications and source records attributed to T Oka.

At least 1,315 records · Page 73Linked to original sources
PubMed1981

Effects of Peripheral monoamines on the monosynaptic reflex neuronal activity of acute spinal cats.

The monosynaptic reflex (MSR) neuronal activity of acute spinal cats was affected not only by monoamine levels in the central nervous system (CNS) but also by peripheral physiological changes, i.e. blood pressure and the temperature of the paraffin pool. Therefore, this report discusses the effects of peripheral monoamines, especially dopamine (DA) or norepinephrine (NE), on the MSR amplitude of acute spinal cats. The results were as follows: 1. Intravenous injections of DA or NE, which did probably not enter the CNS because of the blood-brain barrier, increased MSR neuronal activity. 2. These effects were blocked by the DA receptor antagonist, haloperidol, and the alpha-receptor antagonist, phenoxybenzamine, but not by the beta-receptor antagonist, propranolol. 3. This effect of NE was about 20-fold stronger that that of DA. 4. Larger doses of both amines caused increases in the blood pressure. These results suggested that most hypertensive drugs which cause increases in levels of NE influence the stimulation MSR neuronal activity.

Animals↗
PubMed1981

[Studies of shelf operation on congenital dislocation of hip (author's transl)].

Part I The author examined 62 hips in 58 patients treated by shelf operations, and their long-term results were studied as a follow-up for an average of 10 years. Satisfactory results of the shelf operation were obtained in 51.7% of patients, if over 10 years of age when operated on, but in as many as 72.0%, if under 6 years of age. But as the age of each group changed from that of the time of follow-up age it was impossible to carry out any comparable study between the two groups. Better roentgenographical results appear to be obtained, if this procedure is performed on those over 10 years of age. Part II In an attempt to detect the changes of a hip after the destruction of the outer rim of the acetabulum, experimental studies were undertaken on 50 young rabbits about 40 days after birth. In order to destroy the outer rim of the acetabulum, a small piece of autogeneous iliac bone was embedded in the outer rim of acetabulum where the bone graft is done in human's acetabuloplasty. The results showed that this procedure had no influence on the development of osteoarthritis in a rabbit.

Acetabulum↗
PubMed1981

Effects of fusaric (5-butylpicolinic) acid on the monosynaptic reflex neural activity of cat spinal cord.

It has been demonstrated that most hypertensive drugs which cause increases in levels of norepinephrine influence the stimulation of monosynaptic reflex (MSR) neural activity. However this report discusses the effects of a hypotensive drug, which causes decreases in levels of norepinephrine, on the MSR amplitude of acute spinal cats. This drug is 5-butylpicolinic acid (fusaric acid: FA) which is an effective hypotensive agent and a potent inhibitor of dopamine beta-hydroxylase (approximately 10 times more potent than disurfiram). Intravenous injections of FA increased MSR neural activity in a dose-dependent manner. The FA-induced neural activity was gradually depressed by treatment with haloperidol, a dopamine and/or a alpha receptor blocker and methysergide, a serotonin receptor blocker, respectively. In addition, this neural activity was potentiated by the sequential administration of L-dopa. FA did not cause increases in the blood pressure but inhibit the synthesis of norepinephrine from dopamine. These results suggest that not only hypertensive but also hypotensive drugs can affect the increase of MSR neural activity, and dopamine plays an important role in FA-induced neural activity.

Animals↗
PubMed1980

Vanadate enhances the stimulatory action of insulin on DNA synthesis in cultured mouse mammary gland.

In order to assess the importance of ions in the regulation of mammary epithelial cell proliferation, the effect of various polyvalent ions was examined on insulin- and lithium-ion-dependent DNA synthesis in mouse mammary gland from virgin mice cultured in a serum-free, chemically defined medium. Addition of 2 to 10 microM orthovanadate enhanced the stimulatory effect of insulin on DNA synthesis in cultured tissue. Similar results were obtained with metavanadate. In contrast, vanadate did not augment Li+-stimulated DNA synthesis but rather inhibited this process. Vanadate by itself caused only a slight stimulation of DNA synthesis. These results indicate that vanadate acts as a co-mitogen in insulin-stimulated DNA synthesis in cultured mammary cells and suggest that the mitogenic action of insulin involves an ion-dependent path which may be common to the actions of vanadate and lithium ion.

Animals↗
PubMed1980

Putrescine and the regulation of S-adenosyl-L-methionine decarboxylase in cultured mouse mammary gland.

The activity of S-adenosyl-L-methionine decarboxylase (S-adenosyl-L-methionine carboxy-lyase, EC 4.1.1.50) purified from mouse mammary gland can be stimulated by physiological concentrations of putrescine (Ka = 5 x 10(-7) M). In contrast, the elevation of the intracellular concentrations of putrescine in cultured mouse mammary tissue by exogenous addition of putrescine or by cultivation of the tissue in hypotonic medium results in the decrease in both the activity and the amount of the enzyme in tissue. Conversely, the addition of 1 mM alpha-methyl ornithine, an inhibitor of ornithine decarboxylase, causes augmentation of the activity and the amount of S-adenosyl-L-methionine decarboxylase, despite its inhibitory action on insulin-stimulated increase in the concentration of putrescine. These data suggest that putrescine can act as a 'negative' regulator of the enzyme in this system.

Adenosylmethionine Decarboxylase↗
PubMed1980

Regulation of ornithine decarboxylase in cultured mouse mammary gland by the osmolarity in the cellular environment.

The biphasic increase of ornithine decarboxylase activity in mouse mammary gland in organ culture occurs with a hormone-independent first peak and a hormone-dependent second peak. The data presented indicate that a change in the osmolarity of the cellular environment is the major contributing factor for the emergence of the hormone-independent ornithine decarboxylase activity in mammary explants. Thus, incubation of mammary explants for 3 h in a medium diluted 53% with distilled water results in approx. 1000-fold stimulation of enzyme activity over the initial level, whereas a similar dilution of the medium with 0.18 M NaCl or 0.3 M sucrose blocks the increase. The increase in enzyme activity is similarly affected by a reduction of the concentration of NaCl in the culture medium. The hypoosmotic stimulation of ornithine decarboxylase activity appears to be affected at a posttranscriptional level, and is enhanced further by the actions of insulin and prolactin. The hypoosmotic enhancement of ornithine decarboxylase activity produces a large increase in the intracellular concentration of putrescine in mammary explants. However, neither the concentration of spermidine and spermine nor the activity of S-adenosyl-L-methionine decarboxylase is affected. In addition, studies of putrescine transport in mammary explants show that hypotonicity causes an increase in the rate of influx and a decrease in efflux of putrescine with enhancement of intracellular putrescine accumulation. On the other hand, the uptake of spermidine, spermine, amino acids, sugar, and a lipophilic cation, triphenylmethylphosphonium is unaffected. These data suggest a possibility that osmotic alteration in cellular environment causes an incresed need for putrescine in mammary cells, resulting in stimulation of ornithine decarboxylase activity, which may represent a cellular mechanism for maintaining the homeostasis of the intracellular cationic environment.

Animals↗
PubMed1980

alpha-Lactalbumin-casein induction in virgin mouse mammary explants: dose-dependent differential action of cortisol.

The interplay of insulin, cortisol, and prolactin induces synthesis of casein and alpha-lactalbumin in cultured mammary explants from mature virgin mice. A striking difference has been found between the optimal concentrations of cortisol required for maximal induction of the two milk proteins in vitro: 3 x 10(-8) molar for alpha-lactalbumin and 3 x 10(-6) molar for casein. Moreover, 10(-7) to 10(-5) molar cortisol caused progressive inhibition of alpha-lactalbumin accumulation. Such differential actions of cortisol may partly account for the asynchronous synthesis of the two proteins during pregnancy.

Animals↗
PubMed1980

Purification and characterization of mouse alpha-lactalbumin and preparation of its antibody.

alpha-Lactalbumin was purified to apparent homogeneity from mouse milk by combined use of gel filtration, chromatography on DEAE-cellulose and hydroxyapatite, and concanavalin A-Sepharose affinity chromatography. Mouse alpha-lactalbumin exists in several species with different charges and in two molecular-size forms. The smaller form, which constituted over 90% of total alpha-lactalbumin, included two major and two minor species, each of which showed different electrophoretic mobility on polyacrylamide-gel electrophoresis, but gave the same single band on sodium dodecyl sulphate/polyacrylamide-gel electrophoresis in two different buffer systems and over the range 10-15% acrylamide concentrations. The molecular weight was estimated as 14 100. The two major species of the smaller form had the same amino acid composition and contained no significant amount of carbohydrate. The larger form of alpha-lactalbumin, consisting of two species with different charges, was present in a small amount (less than 10%) in the milk and was isolated by its ability to interact with concanavalin A-Sepharose. Each of the two species also gave the same single band of apparent mol.w.t 18 500 on sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. However, this value may be anomalous, since this larger form appears to be glycosylated, and glycoproteins can behave anomalously on sodium dodecyl sulphate/polyacrylamide gels by binding less sodium dodecyl sulphate. All species of mouse alpha-lactalbumin from milk were active in the lactose synthase reaction and showed identical immunological properties, as determined by the mono-specific antibody prepared against the small major species. The presence of both the larger and the smaller forms, each in a percentage concentration similar to that found in milk, was also demonstrated in alpha-lactalbumin induced by hormones in organ cultureof pregnant-mouse mammary gland.

Amino Acids↗