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Biomedical subjects

I Jansson

Publications and source records attributed to I Jansson.

At least 55 records · Page 3Linked to original sources
PubMed1989

Characterization of the antinociception induced by intrathecally administered carbachol.

The antinociceptive effect of intrathecally administered carbachol at the L1/L2 level in the rat was evaluated using the tail immersion test. A dose dependent increase in the nociceptive reaction times was evident following intrathecal carbachol in the dose range of 2.5-15 micrograms. At doses of 20 micrograms and above, although still effective in the test, motor impairment was pronounced. The antinociception was antagonized with atropine, and with either pirenzepine (PZ) or AFDX 116, which are selective M1 and M2 muscarinic receptor blocking drugs, respectively. Spinal cholinergic pain modulation was also studied in rats pretreated with DSP4 (N-2-chloroethyl-N-ethyl-2-bromobenzylamine), which causes a selective depletion of the noradrenergic nerve fibres in the CNS. The increased latency times after spinal carbachol were attenuated in animals depleted of spinal noradrenaline by DSP4. In conclusion, spinal analgesia by carbachol in the rat may therefore be mediated through both M1 and M2 muscarinic receptor stimulation in the spinal cord. It is also concluded that this spinal cholinergic pain modulation is interacting with spinal noradrenergic nerve terminals, but that the mechanism of the interaction remains to be established.

Analgesics↗
PubMed1988

Reductive metabolism of halothane by purified cytochrome P-450.

The reductive metabolism of halothane was determined using purified RLM2, PBRLM4 and PBRLM5 forms of rat liver microsomal cytochrome P-450. The metabolites, 2-chloro-1,1,1-trifluoroethane (CTE) and 2-chloro-1,1-difluoroethylene (CDE), were determined. All three forms of cytochrome P-450 produced CTE with relatively small differences in its production among the various forms. There were major differences, however, in the production of CDE, with PBRLM5 being the most active. PBRLM5 was also the only form to show the development of a complex between halothane and cytochrome P-450. This complex absorbed light maximally at 470 nm. The complex formation and the production of CDE by PBRLM5 were stimulated by the addition of cytochrome b5. Cytochrome b5 had no effect on CDE production by PBRLM4 and inhibited the production of both CTE and CDE by RLM2. These results show that the two-electron reduction of halothane by cytochrome P-450 was catalyzed by the PBRLM5 form and that cytochrome b5 stimulated the transfer of the second electron to halothane through PBRLM5, but not RLM2 or PBRLM4.

Animals↗
PubMed1988

Regioselective hydroxylation of prostaglandins by constitutive forms of cytochrome P-450 from rat liver: formation of a novel metabolite by a female-specific P-450.

Previous studies demonstrated that liver microsomes from untreated rats catalyze the omega, omega-1, and omega-2 hydroxylation of prostaglandins [K. A. Holm, R. J. Engell, and D. Kupfer (1985) Arch. Biochem. Biophys. 237, 477-489]. The current study examined the regioselectivity of hydroxylation of PGE1 and PGE2 by purified forms of P-450 from untreated male and female rat liver microsomes. PGE1 was incubated with a reconstituted system containing cytochrome P-450 RLM 2, 3, 5, 5a, 5b, 6, or f4, NADPH-P-450 reductase, and dilauroylphosphatidylcholine in the presence or absence of cytochrome b5. Among the P-450 forms examined, only RLM 5 (male specific), 5a (present in both sexes), and f4 (female specific) yielded high levels of PGE hydroxylation. With PGE1, RLM 5 catalyzed solely the omega-1 hydroxylation and 5a catalyzed primarily the omega-1 and little omega and omega-2 hydroxylation. By contrast, f4 effectively hydroxylated PGE1 and PGE2 at the omega-1 and at a novel site. Based on retention on HPLC and on limited mass fragmentation, we speculate that this site is omega-3 (i.e., 17-hydroxylation). Kinetic analysis of PGE1 hydroxylation demonstrated that the affinity of f4 for PGE1 is approximately 100-fold higher than that of RLM 5; the Km values for f4, monitoring 19- and 17-hydroxylation of PGE1, were about 10 microM. Surprisingly, cytochrome b5 stimulated the activity of RLM 5a and f4, but not that of RLM 5. Hydroxylation of PGE2 by RLM 5 was at the omega, omega-1, and omega-2 sites, demonstrating a lesser regioselectivity than with PGE1. These findings show that the constitutive P-450s differ dramatically in their ability to hydroxylate PGs, in their regioselectivity of hydroxylation, and in their cytochrome b5 requirement.

Animals↗
PubMed1987

Fingerprinting rat liver microsomal cytochromes P-450 as a means of delineating sexually distinctive forms.

The cytochrome P-450 fraction of microsomes separated on lauric acid AH-Sepharose 4B columns contains about 75% of the microsomal P-450. This was fingerprinted by means of two dimensional isoelectric focusing/SDS-PAGE. Separation of the fraction by highly reproducible, standard procedures on carboxymethyl Sepharose CL6B into four fractions allowed ready isolation and purification of seven forms of P-450, RLM2, 2b, 3, f4, 5, 5a and f5a. Comparison of the four fractions CMI, CMII, CMIII and CMIV revealed qualitative differences in the proteins contained in CMI and CMII of male and female rats. Identification of these proteins revealed RLM2, present in the CMI fraction of adult male rats, is not present in detectable levels in the comparable fraction from females. Similarly, RLM3 and 5 were present in the CMII fraction of male rats but could not be detected in the corresponding fraction of females. Instead, another protein, fRLM4, was found in the females. RLM5a, found in the CMII fraction of males, was also present in females. Examination of the physical properties of these P-450 proteins revealed those isolated in the CMI and CMII fractions to have fairly neutral isoelectric points (7.1-7.6). Based upon the NH2-terminal amino acid sequence, three classes of constitutive forms of P-450 can be recognized. All of the constitutive forms have methionine in position one and leucine in position seven. By comparing sequence homologies, RLM2 and 2b form one sub-class, RLM3, f4 and 5 form a second sub-class, and P-450f and RLM5a form a third sub-class.

Animals↗
PubMed1987

Inverse relationship between cytochrome P-450 phosphorylation and complexation with cytochrome b5.

Cytochrome P-450 LM2 purified from rabbit liver microsomes has been shown to be a substrate for cAMP-dependent protein kinase. Cytochrome b5, in contrast, was a very poor substrate for cAMP-dependent protein kinase, although it stimulated the activity of the kinase toward histone. When purified rabbit cytochrome b5 was mixed with purified LM2, phosphorylation of LM2 by cAMP-dependent protein kinase was inhibited approximately 80-90%. Recently, a functional covalent complex of cytochrome b5 and LM2 was prepared and purified to homogeneity (P.P. Tamburini and J.B. Schenkman (1987) Proc. Natl. Acad. Sci. USA 84, 11-15). When present as a covalent complex with cytochrome b5, the phosphorylation of LM2 in the complex by cAMP-dependent protein kinase was also inhibited about 80-90% relative to an equivalent amount of LM2 alone. On the other hand, when the LM2 was phosphorylated prior to interaction with cytochrome b5, the ability of the latter to perturb the spin equilibrium of LM2 and oxidation of p-nitroanisole by the LM2 was diminished to an extent comparable to the degree of phosphorylation. The results suggest either that the phosphorylation site on LM2 may be within the cytochrome b5 binding site or that phosphorylation and cytochrome b5 cause mutually exclusive conformational changes in LM2. In addition, eight different forms of cytochrome P-450 from the rat (RLM2, RLM3, fRLM4, RLM5, RLM5a, RLM5b, RLM6, and PBRLM5) were examined as potential substrates for cAMP-dependent protein kinase under the same conditions. Maximal phosphorylation of about 20 mol% was obtained with LM2, and about half as much with PBRLM5. The low extent of phosphorylation of LM2 was not due to the prior presence of phosphate on the enzyme since LM2, as isolated, contains less than 0.1 mol phosphate/mol of enzyme. The other forms of cytochrome P-450 tested showed little or no phosphorylation in vitro despite the presence of a cAMP-dependent protein kinase phosphorylation sequence on at least two of them.

Animals↗
PubMed1987

Blood-to-tissue transport of albumin in rat fibrosarcomas at two different implantation sites.

Albumin clearance and blood flow were measured in normal tissues and in fibrosarcomas by means of a multiple tracer method in intact male rats. Sarcomas implanted in testes had higher albumin clearances than the same tumours implanted in skeletal muscle, 59 and 26 microliters min-1 per 100 g, respectively. Albumin extraction (defined as the ratio of albumin clearance to plasma flow) was found to be 1 x 10(-4) - 14 x 10(-4) in normal tissues. Fibrosarcomas in muscle showed high extractions (24 x 10(-4)), especially in the central portions (96 x 10(-4)), where the extraction was similar to that in tumours implanted in the testes (111 x 10(-4)). The high albumin extraction in poorly perfused central parts of the muscle-implanted tumours and in the similarly insufficiently perfused testicular sarcomas is probably due to an increased endothelial permeability of the exchange vessels and not to an increased capillary exchange surface area compared with the better-perfused peripheral parts of the muscle-implanted tumours. The latter tissue also had a high albumin clearance, however, in the range of that of maximally dilated skeletal muscle vasculature, possibly reflecting a large functional capillary surface area.

Albumins↗
PubMed1987

High-energy phosphates and surface oxygen pressure fields in skeletal muscle after high-energy trauma.

The effect of a high energy missile trauma on energy metabolism and tissue oxygenation in uninjured parts of skeletal muscle was studied in anaesthetized pigs up to 72 hours after the trauma. High energy phosphates (HEP) were measured in muscle biopsies, and muscle tissue oxygenation was measured as muscle surface oxygen pressure fields by an oxygen electrode. In the traumatized group significantly decreased levels of HEP were found in spite of normal tissue oxygenation 72 hours after the trauma. In the control group both the HEP and the muscle tissue oxygenation were unchanged compared to the pretrauma situation. Decreased synthesis of HEP due to tissue hypoxia or inadequate nutrition could not account for the difference between the control and the trauma group. It was suggested that hypermetabolism induced by the high energy trauma caused increased utilization and thereby decreased concentrations of the HEP 72 hours after the trauma. It was also concluded that the general posttraumatic metabolic changes found in uninjured parts of the muscle tissue differed from the local changes of traumatized muscle described by other investigators, and therefore probably were caused by other mechanisms.

Adenosine Diphosphate↗
PubMed1986

Differences in the spectral interactions between NADPH-cytochrome P-450 reductase and a series of cytochrome P-450 enzymes.

The interaction between NADPH-cytochrome P-450 reductase and a series of cytochrome P-450 isozymes was investigated using UV-visible spectrophotometry. In the absence of substrate the interactions between the reductase and RLM3, RLM5, and RLM5a were tight, exhibiting sub-micromolar dissociation constants and resulted in type I spectra of varying magnitude from which the following increases in the proportion of high spin hemoprotein were calculated; RLM3 (7%), RLM5 (36%), RLM5a (6%), LM2 (29%), RLM2 (0%). Preincubation of LM2 with its type I substrate benzphetamine increased the affinity of the cytochrome for the reductase. Using initial estimates of the P-450 spin states in the absence of reductase in conjunction with the spectral binding data and equations relating these parameters to the microequilibria for the association of reductase with high or low spin P-450, RLM3, RLM5, RLM5a and LM2 were shown to bind significantly more tightly to high spin P-450. The relevance of this data to the understanding of spin state influence on P-450 reduction is discussed.

Animals↗
PubMed1986

Vascular reactivity to norepinephrine of 7,12-dimethylbenz(a)anthracene-induced rat mammary tumors and normal tissue as studied in vitro.

Vascular reactivity to norepinephrine has been studied in dimethyl-benz(a)anthracene-induced rat mammary neoplasia and compared with that of skeletal muscle, salivary gland, kidney, and uterus by means of an artificial perfusion technique. Perfusion of tissues and organs was measured with the microsphere tracer technique during smooth muscle relaxation and infusion of norepinephrine at two different dose levels. This procedure makes possible a dose-response analysis of several tissues under controlled conditions without confounding endogenous vasoregulation. The tumor vascular bed has a low perfusion capacity during smooth muscle relaxation and responds rapidly with an increased resistance to norepinephrine infusion. The results indicate a hypersensitivity, although the relative maximal constrictor response is equal to or less than that of other vascular beds studied.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1985

Kinetics of cytochrome P-450 reduction: evidence for faster reduction of the high-spin ferric state.

Results are presented that support our hypothesis [Backes, W. L., Sligar, S. G., & Schenkman, J. B. (1980) Biochem. Biophys. Res. Commun. 97, 860-867] that the multiphasic reduction kinetics of cytochrome P-450 are, in part, due to the spin equilibrium of the ferric hemoprotein. The disappearance of the high-spin charge-transfer band at 650 nm during reduction of the hemoprotein by NADPH was fast, exhibiting a rate constant greater than that of the fast phase of reduction measured by formation of the carbon monoxide adduct. In contrast, the disappearance of the ferric low-spin form of the cytochrome was at a considerably slower rate. A mathematical expression of the fractional content of high-spin cytochrome P-450 was obtained by comparing the ratio of the initial rate of change in the fraction of total oxidized cytochrome remaining to the initial rate of change in the fraction of high-spin ferric P-450 remaining. Results supporting the model were obtained by using both microsomes and purified cytochrome P-450 RLM5. The calculation from experimental data yielded results that were similar to those obtained by different extrapolation methods used for estimation of the amount of high-spin cytochrome P-450, supporting further the proposed relationship between the spin equilibrium and the reduction kinetics of this hemoprotein.

Animals↗
PubMed1985

Purification and characterization of a new form (RLM2) of liver microsomal cytochrome P-450 from untreated rat.

A new cytochrome P-450 isozyme (RLM2) has been purified to electrophoretic homogeneity from liver microsomes of the untreated rat. It has an apparent minimum molecular weight on sodium dodecyl sulfate-polyacrylamide gel electrophoresis of 49,000. Absolute spectrum of the oxidized form indicates that this isozyme is essentially all in the low spin state. The maximum of the reduced CO complex is at 449 nm. Amino-terminal partial amino acid sequence and amino acid composition are different from those of RLM3 and RLM5, two other native forms of cytochrome P-450 previously reported from this laboratory as well as other forms reported in the literature. RLM2 is capable of oxidizing a variety of drug substrates, like benzphetamine and aminopyrine, and to a lesser extent ethoxycoumarin. With the steroid substrate multiple isomeric products are formed differentially. Progesterone is preferentially hydroxylated at the 15-position (15 beta-hydroxylation (34%) and 15 alpha-hydroxylation (13%) of the total) and at the 6 beta-position (21%). The major metabolite when testosterone was the substrate, 15 alpha-hydroxytestosterone, comprised 43% of the total, while a modest amount of 6 beta-hydroxytestosterone (12%) is formed. Another major metabolite (31%) has yet to be unequivocally identified, but is suggested to be 7 beta-hydroxytestosterone. Examination of the substrate dependence of major and minor isomeric metabolites provides evidence for a single substrate-binding site on RLM2. Regardless of the position hydroxylated, a common Km value was obtained. It is suggested that differences in formation of the isomeric and epimeric products relate to differences in distance from the active oxygen center and the position of attack.

Amino Acid Sequence↗
PubMed1985

Experimental posttraumatic pulmonary microembolism. Effects of methylprednisolone on its development.

The effects of methylprednisolone sodium succinate on the course of posttraumatic pulmonary microembolism were studied in pigs submitted to a reproducible high-energy trauma of the limb and then observed under long-term anesthesia. Methylprednisolone sodium succinate (30 mg/kg of body weight) was given one hour after trauma and thereafter every eighth hour during a 72-hour observation period. Intrapulmonary microembolism was quantitatively measured by repeated external detection of chromium 51-labeled platelets and iodine 125-labeled fibrinogen, sequential chest roentgenograms, and morphologic examination of the lungs post mortem. Methylprednisolone delayed the onset of pulmonary roentgenogram changes and modulated Pao2 and platelet count reductions, but, at the end of the observation period, the signs of microembolism changes were as pronounced as in the nontreated traumatized pigs. Methylprednisolone thus did not prevent posttraumatic pulmonary microembolism in this experimental situation.

Animals↗
PubMed1985

The effect of postoperative external radiotherapy on cervical carcinoma stage IB and IIA.

Among 344 patients operated after intracavitary irradiation of cervical carcinoma stage IB and IIA, 55 had positive nodes in the operation specimen, 16 of these received no postoperative irradiation, 22 received pelvic irradiation without a boost dose to positive nodes, and 17 also received a boost. The crude 5-year survival was 52% for these 55 high-risk patients. All 3 patients with adenocarcinoma died. For squamous-cell carcinoma postoperative irradiation gave a later relapse and less distant metastases, but survival was not approved. Postoperative irradiation with a boost added, resulted in 3 recurrences among 16 patients, none in the treated volume, and only one complication. The numerically improved survival of this small group was not statistically significant, however. A randomized trial with and without postoperative irradiation with a boost dose, requiring 1100-1200 operated patients, would answer the question whether the observed improval is significant or not.

Adult↗
PubMed1985

Occurrence, nature and treatment of urinary incontinence in a 70-year-old female population.

An intervention trial using oral oestriol to treat urinary incontinence was performed in a number of patients taken from a representative sample of 562 women aged 75 yr. The clinical series consisted of 34 patients who took part in a double-blind crossover study of the possible effects of oestriol, given in a single daily dose of 3 mg, and of a placebo over a period of 3 mth. The clinical examinations included bacteriological cultures and an assessment of the degree of atrophy of the surface membranes in the vagina. In most patients, oestriol was effective in reversing the atrophy. The clinical effect was excellent in urgency and mixed incontinence, but not in stress incontinence.

Aged↗