Search PubMed⌕ Search

Biomedical subjects

J R Martin

Publications and source records attributed to J R Martin.

At least 199 records · Page 11Linked to original sources
PubMed1981

6'-N-methylfortimicins A and B and 6',6'-di-N-methylfortimicins A and B.

Selective 6'-N-alkylation of 1,2'-di-N-benzyloxycarbonylfortimicin B was effected by both catalytic and chemical reductive alkylation in the presence of aldehydes. These facile selective 6'-N-alkylations were used as the basis of the preparations of the 6',6'-di-N-methylfortimicins A and B, and the 6'-N-methylfortimicins A and B. Of these new 6'-N-methylated fortimicins, only 6'-N-methylfortimicin A has appreciable antibacterial activity, which was about half that of fortimicin A.

Aminoglycosides↗
PubMed1980

Regional 5-HT analysis in Roman high- and low-avoidance rats following MAO inhibition.

5-HT and 5-HIAA levels were investigated in three brain regions of Roman high- and low-avoidance rats, following 10, 30 and 60 min of MAO inhibition (pargyline injection). Higher levels of 5-HT in the cortex at 30 and 60 min, as well as a higher disappearance rate of 5-HIAA in the midbrain/medulla region were exhibited by Roman high-avoidance rats, thus further characterizing the differences previously observed in whole brain 5-HT synthesis between these selected rat lines.

Animals↗
PubMed1980

Nicotine and amphetamine: differential tolerance and no cross-tolerance for ingestive effects.

Rats chronically treated twice daily with nicotine (0.4 mg/kg, SC) or d,1-amphetamine (1.5 mg/kg, SC) exhibited different patterns of anorexia, hypodipsia, and body weight loss. Amphetamine-treated rats developed tolerance to these ingestive effects and to weight loss, whereas nicotine-injected rats did not. There was little, if any, evidence for cross-tolerance when the drugs were switched between the two groups. These results indicate that different mechanisms underlie the ingestive effects of nicotine and amphetamine.

Amphetamine↗
PubMed1980

Exploratory behaviour of rats at oestrus.

Twenty-seven nulliparous RHA/Verh female rats received a daily-6-min test in a familial maze. The complex maze was of the Dashiell type and included a small illuminated central arena. It was demonstrated that these female rats more rapidly patrolled the maze at oestrus than on either of the two days preceding or following oestrus. Consistent with a number of earlier reports, it was also shown that general locomotor activity increased, body weight decreased, and the frequency of entry into the illuminated maze centre increased at oestrus.

Animals↗
PubMed1980

4-N-acylfortimicins B and the preparation of fortimicin A from fortimicin B.

Selective 4-N-acylation of fortimicin B (2) has been accomplished by 4-N-acylation of 1,2',6'-tri-N-benzyloxycarbonylfortimicin B (4) followed by hydrogenolysis of the N-protecting benzyloxycarbonyl groups. In this manner, fortimicin B was converted into fortimicin A (1), and a series of 4-N-acylfortimicins B (3) was prepared for antibacterial assay. The key intermediate, 1,2',6'-tri-N-benzyloxycarbonylfortimicin B, was prepared either directly from fortimicin B or by converting fortimicin A into 1,2',6',2''-tetra-N-benzyloxycarbonylfortimicin A (6a), followed by selective hydrolysis of the 4-N-(N-benzyloxycarbonyl)glycyl group of the latter.

Acylation↗
PubMed1980

Multivariate analysis of meal patterning in intact and vagotomized rabbits.

Meal patterns of female rabbits were measured throughout a 12:12 hr light/dark cycle and subjected to a multivariate-univariate analysis. Increased food intake occurring during the first 6 hr of dark was attributed to increased meal frequency and feeding rate, while that found during the last 6 hr of dark was attributed to increased meal duration and meal size. Meal patterning was also nonhomogeneous between the 6-hr periods in the light portion of the cycle. Experiment 2 demonstrated the times of day when feeding patterns of vagotomized animals are different from those of intact animals and, further, delineated the relevant variables that are altered by vagotomy. Immediately following light offset, vagotomized animals were distinguished from intact animals by sloer feeding rate and decreased food intake. Immediately following light onset, vagotomized animals were distinguished from intact animals by decreased feeding frequency, increased meal duration, and increased satiety ratio. During the 6 hr immediately preceding light onset or offset, none of the variables could discriminate the feeding patterns of intact animals from those of vagotomized animals.

Animals↗
PubMed1980

Synthesis of 3-O-demethylfortimicins.

Treatment of fortimicin B with lithium in ethylamine gave 3-O-demethylfortimicin B. The latter was converted by methodology developed with fortimicin B to 3-O-demethylfortimicin A, 4-N-sarcosyl-3-O-demethylfortimicin B, 4-N-beta-alanyl-3-O-demethylfortimicin B, and 4-N-(beta-aminoethyl)-3-O-demethylfortimicin B. 3-O-demethylfortimicin A and the 4-N-acyl-3-O-demethylfortimicins B had appreciably higher antibacterial activities than the corresponding parent fortimicins. Most significant was the increased activity of 3-O-demethylfortimicin A relative to fortimicin A against a variety of strains of Pseudomonas aeruginosa.

Aminoglycosides↗
PubMed1980

synthesis of 2-deoxyfortimicins and 1-deamino-2-deoxy-2-epi-aminofortimicins via 2-O-methanesulfonylfortimicin B.

The synthesis of 2-deoxyfortimicins A (15) and B (11) and 1-deamino-2-deoxy-2-epi-amino-fortimicins A (18) and B (12) is described. Two routes have been developed for synthesis of the key intermediate 2-O-methanesulfonylfortimicin B (7). One route involves selective blocking of fortimicin B with B-benzyloxycarbonyl groups followed by formation of a 4,5-salicylaldehyde oxazolidine derivative. Subsequent mesylation followed by deblocking gave 7. A more efficient route to 7 involves concomitant salicylaldehyde Schiff base and 4,5-oxazolidine formation followed by mesylation and hydrolysis. The formation of 1,2(R)-epiminofortimicin B (8) from 7 followed by RANEY nickel reduction gave 2-deoxyfortimicin B and 1-deamino-2-deoxy-2-epi-aminofortimicin B, which were converted to the corresponding fortimicin A derivative by selective N-blocking, N-acylation and subsequent deblocking. The antibacterial activities of the new fortimicin A derivatives are presented.

Aminoglycosides↗
PubMed1979

Computer-compatible system for continuous volumetric measurement of water consumption?

An inexpensive drinkometer system is described that is compatible with most data acquisition systems and can be used for continuously monitoring the drinking pattern of laboratory animals. The change in electrical inductance resulting from the descent of a free-floating ferrite unit through a drinking tube, surrounded by a double coil, is converted to a signal proportional to the volume of fluid consumed.

Animals↗
PubMed1979

An ultrastructural study of the cerebrospinal fluid in visna.

An electron microscopic examination was done on 8 samples of cerebrospinal fluid (CSF) from Icelandic sheep infected by the intracerebral route with visna virus. The specimens were collected 1 month, 2 months, and 4 years after infection. A differentail cell count done on low-power electron micrographs showed that the cellular exudate was composed of mononuclear cells mainly macrophages and lymphocytes with a few plasma cells. Macrophages were with one exception more numerous than lymphocytes and an increased proportion of macrophages showed evidence of phagocytosis with time after infection. Reactive lymphocytes were in general more numerous than small lymphocytes. Various stages in the maturation of plasma cells were observed. The cellular composition in the CSF is compatible with the view that visna is an immunopathological process. Myelin figures and fragments of myelinated axons were observed in two specimens indicating an active myelin-breakdown. The possibility that escape of myelin into the CSF may lead to sensitization to myelin antigens and perpetuation of this chronic neurologic affection is discussed. Visna virions could not be demonstrated.

Animals↗