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At least 955 records · Page 53Linked to original sources
PubMed1989

[The synthesis of 4'-(2-carboxyethyl)phenyl trans-4-aminomethyl cyclohexane carboxylate hydrochloride (cetraxate hydrochloride) by means of enzymatic debenzylation].

Cetraxate hydrochloride (1) (antiulcer agent) has been industrially produced by the chemical protective method of p-hydroxy propionic acid derivatives. Screening of enzymes which quantitatively hydrolyzed cetraxate benzyl ester hydrochloride (2) into 1 was undertaken to establish a novel enzymatic method of production of 1. It was found that the enzyme activity for debenzylation of 2 is contained in cellulase enzymes originated from Aspergillus sp. Lower alkyl groups or phenyl groups of p-hydroxy propionic acid derivatives are likewise selectively hydrolyzed by the cellulase enzyme. This enzymatic synthetic method is very useful for the industrial preparation of 1.

Anti-Ulcer Agents↗
PubMed1981

Effects of tranexamic acid and urokinase on hematogenous metastases of Lewis lung carcinoma in mice.

When Lewis lung carcinoma with low thromboplastic and low fibrinolytic activities was implanted subcutaneously to mice, administration of tranexamic acid inhibited metastasis formation in the lungs. This effect was considered to be mediated by prevention of cell release from the implanted sites. Fibrin formation around tumor cells in the vessels of primary foci was observed in the mice given tranexamic acid. On the other hand, urokinase significantly enhanced pulmonary metastases and many free tumor cells were observed intravascularly in primary foci of the mice given urokinase.

Animals↗
PubMed1995

Inactivation of gamma-aminobutyric acid aminotransferase by L-3-chloroalanine hydroxamate.

The mechanism of inactivation of gamma-aminobutyric acid aminotransferase (GABA-AT) by L-3-chloroalanine hydroxamate (1) was investigated. Inactivation of [3H]PLP-reconstituted GABA-AT with 1 followed by denaturation gave no PMP or enamine adduct to the PLP; however, a new unknown metabolite was observed which was identical to the metabolite formed upon inactivation of GABA-AT by L-cycloserine. Time-dependent inactivation occurs, but the kinetics are second order; the rate of inactivation increases with time. After inactivation occurs the addition of fresh enzyme results in a faster rate of inactivation than prior to the initial inactivation. This indicates that the actual inactivator is generated from L-3-chloroalanine hydroxamate, and is not L-3-chloroalanine hydroxamate itself. Added gabaculine-inactivated enzyme to fresh enzyme does not increase the rate of inactivation, suggesting that the conversion of L-3-chloroalanine hydroxamate to the active form is not catalyzed by peripheral amino acid residues. L-3-Chloroalanine hydroxamate was shown to undergo buffer-catalyzed cyclization to L-cycloserine, which is the actual inactivator of GABA-AT.

4-Aminobutyrate Transaminase↗
PubMed1976

Traumatic hyphaema treated with the antifibrinolytic drug tranexamic acid.

During the year 1975 (Jan. 1st-Dec. 31st) 72 patients, consecutively admitted to the eye department of Arhus Kommunehospital with traumatic hyphaema, were treated with the antifibrinolytic drug tranexamic acid. Secondary haemorrhage occurred in one case. This incidence of secondary haemorrhage (1.4%) seems to be the lowest on record. A group of patients from the period 1965-1968, treated identically with the exception of the tranexamic acid, were selected for comparison. This group of 135 patients included 9 cases (6.7%) with a secondary haemorrhage. The difference between these two groups is statistically significant (P less than 0.05).

Adolescent↗
PubMed1979

Tranexamic acid in massive haemorrhage from the upper gastrointestinal tract: a double-blind study.

In a double-blind trial of tranexamic acid in massive upper gastrointestinal haemorrhage, 76 patients were treated with the active drug and 73 patients with placebo. The doses were 1 g intravenously six times daily for a maximum of 3 days, followed by 1.5 g orally four times daily for a maximum of 4 days. The treatment group and the placebo group were comparable with respect to mean age, diagnoses and laboratory tests but differed slightly with respect to sex and alcohol consumption. The transfusion requirement in the treatment group was less than in the placebo group during the first days after admission, the difference being significant on the second day after admission. Ten patients in the treatment group and 18 patients in the placebo group were operated on. Eleven patients in the treatment group and 12 patients in the placebo group died. In the tranexamic-acid-treated group fewer operations were performed and significantly less blood was needed. It therefore seems highly likely that tranexamic acid has a beneficial effect, although small.

Aged↗
PubMed2002

Molecular cloning and characterization of the human voltage-gated calcium channel alpha(2)delta-4 subunit.

The voltage-gated calcium channel is composed of a pore-forming alpha(1) subunit and several regulatory subunits: alpha(2)delta, beta, and gamma. We report here the identification of a novel alpha(2)delta subunit, alpha(2)delta-4, from the expressed sequence tag database followed by its cloning and characterization. The novel alpha(2)delta-4 subunit gene contains 39 exons spanning about 130 kilobases and is co-localized with the CHCNA1C gene (alpha(1C) subunit) on human chromosome 12p13.3. Alternative splicing of the alpha(2)delta-4 gene gives rise to four potential variants, a through d. The open reading frame of human alpha(2)delta-4a is composed of 3363 base pairs encoding a protein with 1120 residues and a calculated molecular mass of 126 kDa. The alpha(2)delta-4a subunit shares 30, 32, and 61% identity with the human calcium channel alpha(2)delta-1, alpha(2)delta-2, and alpha(2)delta-3 subunits, respectively. Primary sequence comparison suggests that alpha(2)delta-4 lacks the gabapentin binding motifs characterized for alpha(2)delta-1 and alpha(2)delta-2; this was confirmed by a [(3)H]gabapentin-binding assay. In human embryonic kidney 293 cells, the alpha(2)delta-4 subunit associated with Ca(V)1.2 and beta(3) subunits and significantly increased Ca(V)1.2/beta(3)-mediated Ca(2+) influx. Immunohistochemical study revealed that the alpha(2)delta-4 subunit has limited distribution in special cell types of the pituitary, adrenal gland, colon, and fetal liver. Whether the alpha(2)delta-4 subunit plays a distinct physiological role in select endocrine tissues remains to be demonstrated.

Acetates↗
PubMed1998

Effects of 3-mercaptopicolinic acid and a derivative of chlorogenic acid (S-3483) on hepatic and islet glucose-6-phosphatase activity.

Glucose-6-phosphatase activity was measured in hepatic microsomes and in pancreatic islets from ob/ob mice. In hepatic microsomes vanadate, phlorizin, 3-mercaptopicolinic acid and a derivative of chlorogenic acid (S-3483) inhibited the translocase activity of the enzyme, vanadate in addition inhibited hydrolase activity. In islets, vanadate inhibited both components of the enzyme, phlorizin inhibited only hydrolase activity while 3-mercaptopicolinic acid and compound S-3483 were without effect. Similarly, when islets were incubated with 3H2O and unlabeled glucose, the incorporation of 3H into medium glucose was inhibited by vanadate and phlorizin, but not by 3-mercaptopicolinic acid and S-3483. These findings suggest that, as with glucokinase, different isoenzymes of glucose-6-phosphatase are present in islets and liver.

Animals↗
PubMed1984

Mechanisms of enzymatic and acid-catalyzed decarboxylations of prephenate.

The prephenate dehydrogenase activity of the bifunctional enzyme chorismate mutase-prephenate dehydrogenase from Escherichia coli catalyzes the oxidative decarboxylation of both prephenate and deoxoprephenate, which lacks the keto group in the side chain (V 78% and V/K 18% those of prephenate). Hydride transfer is to the B side of NAD, and the acetylpyridine and pyridinecarboxaldehyde analogues of NAD have V/K values 40 and 9% and V values 107 and 13% those of NAD. Since the 13C isotope effect on the decarboxylation is 1.0103 with deuterated and 1.0033 with unlabeled deoxoprephenate (the deuterium isotope effect on V/K is 2.34), the mechanism is concerted, and if CO2 has no reverse commitment, the intrinsic 13C and deuterium isotope effects are 1.0155 (corresponding to a very early transition state for C-C bond cleavage) and 7.3, and the forward commitment is 3.7. With deoxodihydroprephenate (lacking one double bond in the ring), oxidation occurs without decarboxylation, and one enantiomer has a V/K value 23-fold higher than the other (deuterium isotope effects are 3.6 and 4.1 for fast and slow isomers; V for the fast isomer is 5% and V/K 0.7% those of prephenate). The fully saturated analogue of deoxoprephenate is a very slow substrate (V 0.07% and V/K approximately 10(-5%) those of prephenate). pH profiles show a group with pK = 8.3 that must be protonated for substrate binding and a catalytic group with pK = 6.5 that is a cationic acid (likely histidine). This group facilitates hydride transfer by beginning to accept the proton from the 4-hydroxyl group of prephenate prior to the beginning of C-C cleavage (or fully accepting it in the oxidation of the analogues with only one double bond or none in the ring). In contrast with the enzymatic reaction, the acid-catalyzed decarboxylation of prephenate and deoxoprephenate (t1/2 of 3.7 min at low pH) is a stepwise reaction with a carbonium ion intermediate, since 18O is incorporated into substrate and its epi isomer during reaction in H218O. pH profiles show that the hydroxyl group must be protonated and the carboxyl (pK approximately 4.2) ionized for carbonium ion formation. The carbonium ion formed from prephenate decarboxylates 1.75 times faster than it reacts with water (giving 1.8 times as much prephenate as epi isomer). The observed 13C isotope effect of 1.0082 thus corresponds to an intrinsic isotope effect of 1.023, indicating an early transition state for the decarboxylation step. epi-Prephenate is at least 20 times more stable to acid than prephenate because it exists largely as an internal hemiketal.(ABSTRACT TRUNCATED AT 400 WORDS)

Carbon Isotopes↗
PubMed1998

Role of branched-chain aminotransferase isoenzymes and gabapentin in neurotransmitter metabolism.

Because it is well known that excess branched-chain amino acids (BCAAs) have a profound influence on neurological function, studies were conducted to determine the impact of BCAAs on neuronal and astrocytic metabolism and on trafficking between neurons and astrocytes. The first step in the metabolism of BCAAs is transamination with alpha-ketoglutarate to form the branched-chain alpha-keto acids (BCKAs). The brain is unique in that it expresses two separate branched-chain aminotransferase (BCAT) isoenzymes. One is the common peripheral form [mitochondrial (BCATm)], and the other [cytosolic (BCATc)] is unique to cerebral tissue, placenta, and ovaries. Therefore, attempts were made to define the isoenzymes' spatial distribution and whether they might play separate metabolic roles. Studies were conducted on primary rat brain cell cultures enriched in either astroglia or neurons. The data show that over time BCATm becomes the predominant isoenzyme in astrocyte cultures and that BCATc is prominent in early neuronal cultures. The data also show that gabapentin, a structural analogue of leucine with anticonvulsant properties, is a competitive inhibitor of BCATc but that it does not inhibit BCATm. Metabolic studies indicated that BCAAs promote the efflux of glutamine from astrocytes and that gabapentin can replace leucine as an exchange substrate. Studying astrocyte-enriched cultures in the presence of [U-14C]glutamate we found that BCKAs, but not BCAAs, stimulate glutamate transamination to alpha-ketoglutarate and thus irreversible decarboxylation of glutamate to pyruvate and lactate, thereby promoting glutamate oxidative breakdown. Oxidation of glutamate appeared to be largely dependent on the presence of an alpha-keto acid acceptor for transamination in astrocyte cultures and independent of astrocytic glutamate dehydrogenase activity. The data are discussed in terms of a putative BCAA/BCKA shuttle, where BCATs and BCAAs provide the amino group for glutamate synthesis from alpha-ketoglutarate via BCATm in astrocytes and thereby promote glutamine transfer to neurons, whereas BCATc reaminates the amino acids in neurons for another cycle.

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗
PubMed1972

Tranexamic acid in control of haemorrhage after dental extraction in haemophilia and Christmas disease.

In a double-blind trial tranexamic acid (AMCA, Cyclokapron), 1 g three times a day for five days, significantly reduced blood loss and transfusion requirements after dental extraction in patients with haemophilia and Christmas disease. No side effects were seen in either group of patients. Screening tests showed no toxic action of tranexamic acid on the liver, kidney, or heart.

Adolescent↗
PubMed1981

Antifibrinolysis with tranexamic acid in aneurysmal subarachnoid hemorrhage: a consecutive controlled clinical trial.

A randomized controlled clinical trial was carried out to study the effect of tranexamic acid (AMCA, Cyklokapron; AB Kabi, Stockholm, Sweden) in the prevention of early rebleeding after the rupture of an intracranial aneurysm. The incidence of vasospasm, hydrocephalus, cerebral ischemic and thromboembolic complications, morbidity, and mortality was also evaluated. The series comprises 59 patients, 30 treated with tranexamic acid and 29 controls. The treatment was stopped if there was rebleeding, operation, or discharge from the hospital. There were 6 recurrent hemorrhages in 6 patients in the tranexamic acid-treated group and 11 recurrences in 7 patients in the control group. Recurrent hemorrhages occurred later in tranexamic acid-treated patients than in controls. Five patients in each group died from rebleeding. Five additional treated patients and 2 controls died from cerebral ischemic dysfunction. The results suggest that tranexamic acid may protect patients with ruptured aneurysms from rebleeding for 1 or 2 weeks, but that it also may produce cerebral ischemic complications.

Adult↗
PubMed1987

Tranexamic acid in gastric and duodenal bleeding.

In this prospective, randomized, double-blind study the effect of the antifibrinolytic drug tranexamic acid was compared with that of placebo in 154 patients bleeding from verified benign lesions in the stomach and/or duodenum. Three out of 72 patients receiving tranexamic acid underwent emergency surgery, in contrast to 15 out of 82 in the placebo group (p = 0.010). Nineteen patients receiving placebo rebled during admission, as compared with 10 in the treatment group (p = 0.097). The blood transfusion requirement was significantly reduced by tranexamic acid (p = 0.018). Side effects were seen in six patients, of which an uncomplicated deep venous thrombosis was the most severe. It was concluded that tranexamic acid reduces the blood transfusion requirement and the need for emergency surgery in patients bleeding from a benign gastric or duodenal lesion.

Adult↗
PubMed1989

On the effects of tranexamic acid and its isobenzedrine ester on plasminogen activation and streptokinase induced fibrinolysis.

A comparison between the inhibitory capability of Tranexamic acid (AMCA) and its isobenzedrine ester (IB-AMCA) on the streptokinase and urokinase induced plasminogen activation, indicated in vitro a higher potency of the ester derivative. A peculiar activatory rather than inhibitory effect on the plasminogen activation was exerted by AMCA and aminocaproic acid at relatively low concentrations. Attempts to show in vivo the in vitro observed differences between AMCA and IB-AMCA action are reported.

Animals↗
PubMed1978

Tranexamic acid in the preoperative management of ruptured intracranial aneurysms.

A randomized, controlled clinical trial was carried out to study the effect of tranexamic acid (AMCA, trans-AMCHA) in prevention of early rebleeding after proven rupture of an intracranial aneurysm. The series comprises 46 patients admitted to the hospital within three days after the first bleeding. Twenty-three were treated with tranexamic acid and 23 were controls. Nine patients in the control group and one in the group treated with tranexamic acid had confirmed rebleeding. The incidence of vasospasm, cerebral ischemia and hydrocephalus as well as mortality and morbidity is discussed.

Adult↗
PubMed2001

Gabapentin and gabapentin monohydrate.

Gabapentin [1-(aminomethyl)cyclohexaneacetic acid, C9H17NO2] is a zwitterion in the solid state. Its crystal structure involves extensive hydrogen bonding between the NH3(+) and COO(-) groups of neighboring molecules. The structure of gabapentin monohydrate [1-(aminomethyl)cyclohexaneacetic acid monohydrate, C9H17NO2-H2O] also involves such hydrogen bonding and, in addition, has a hydrogen-bonding network comprising the water molecules and both the NH3(+) and COO(-) groups.

Acetates↗
PubMed1984

Wound healing following dental extractions in rabbits: effects of tranexamic acid, warfarin anti-coagulation, and socket packing.

We have investigated the importance of the coagulation and fibrinolytic systems for wound healing following dental extractions. Four front teeth were extracted in rabbits; wound healing was measured as time until complete epithelial closure. The antifibrinolytic agent tranexamic acid shortened duration of wound healing in normal rabbits. Anti-coagulation with warfarin delayed epithelial closure, which was, however, normalized by simultaneous administration of tranexamic acid, whereas complete packing of the socket with oxidized cellulose had no corrective effect. Apical packing together with tranexamic acid gave normal healing. It is concluded that the quality of the fibrin network within the dental socket determines the rate of wound healing; oxidized cellulose is not an adequate substitute for fibrin.

Alveolar Process↗