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Biomedical subjects

J Hall

Publications and source records attributed to J Hall.

At least 397 records · Page 22Linked to original sources
PubMed1987

The reaction of cytochromes c and c2 with the Rhodospirillum rubrum reaction center involves the heme crevice domain.

In order to define the interaction domain on Rhodospirillum rubrum cytochrome c2 for the photosynthetic reaction center, positively charged lysine amino groups on cytochrome c2 were modified to form negatively charged carboxydinitrophenyl lysines. The reaction mixture was separated into six different fractions by ion exchange chromatography on carboxymethylcellulose and sulfopropyl-Sepharose. Peptide mapping studies indicated that fraction A consisted of a mixture of singly labeled derivatives modified at lysines 58, 81, and 109 on the back of cytochrome c2. Fractions C1, C2, C3, and C4 were found to be mixtures of singly labeled derivatives modified at lysines 9, 13, 75, 86, and 88 on the front of cytochrome c2 surrounding the heme crevice. The photooxidation of the carboxydinitrophenyl-cytochrome c2 derivatives by reaction centers purified from R. rubrum was measured following excitation with a laser pulse. The second-order rate constant of fraction A modified at backside lysines was found to be 2.3 X 10(7) M-1 s-1, nearly the same as that of native cytochrome c2, 2.6 X 10(7) M-1 s-1. However, the rate constants of fractions C1-C4 were found to be 6 to 12-fold smaller than that of native cytochrome c2. These results indicate that lysines surrounding the heme crevice of cytochrome c2 are involved in electrostatic interactions with carboxylate groups at the binding site of the reaction center. The reaction rates of horse heart cytochrome c derivatives modified at single lysine amino groups with trifluoroacetyl or trifluoromethylphenylcarbamoyl were also measured. Modification of lysines 8, 13, 25, 27, 72, 79, or 87 surrounding the heme crevice was found to significantly lower the rate of reaction, while modification of lysines in other regions had no effect. This indicates that the reaction of horse heart cytochrome c with the reaction center also involves the heme crevice domain.

Binding Sites↗
PubMed1987

Reaction of cytochromes c and c2 with the Rhodobacter sphaeroides reaction center involves the heme crevice domain.

In order to define the interaction domain on Rhodobacter sphaeroides cytochrome c2 for the photosynthetic reaction center, positively charged lysine amino groups on cytochrome c2 were modified to form negatively charged (carboxydinitrophenyl)- (CDNP-) lysines. The reaction mixture was separated into several different fractions by ion-exchange chromatography on (carboxymethyl)cellulose. Tryptic digests of these fractions were analyzed by reverse-phase peptide mapping to determine the lysines that had been modified. Fraction A was found to consist of a mixture of singly labeled derivatives modified at lysine-35, -88, -95, -97, and -105 and several other unidentified lysines comprising 32% of the total. Although it was not possible to resolve these derivatives, all of the identified lysines are located on the front surface of cytochrome c2 near the heme crevice. The second-order rate constant for the reaction of native cytochrome c2 with reaction centers was 2.0 X 10(8) M-1 s-1, while that for fraction A was 20-fold less, 1.0 X 10(7) M-1 s-1. This suggests that lysines surrounding the heme crevice of cytochrome c2 are involved in electrostatic interactions with carboxylate groups at the binding site of the reaction center. The reaction rates of horse heart cytochrome c derivatives modified at single lysine amino groups with trifluoroacetyl or trifluoromethylphenylcarbamoyl were also measured. Modification of lysine-8, -13, -27, -72, -79, and -87 surrounding the heme crevice significantly lowered the rate of reaction, while modification of lysines in other regions had no effect. This indicates that the reaction of horse heart cytochrome c with the reaction center also involves the heme crevice domain.

Amino Acid Sequence↗
PubMed1987

The binding domain on horse cytochrome c and Rhodobacter sphaeroides cytochrome c2 for the Rhodobacter sphaeroides cytochrome bc1 complex.

The interaction of the Rhodobacter sphaeroides cytochrome bc1 complex with Rb. sphaeroides cytochrome c2 and horse cytochrome c was studied by using specific lysine modification and ionic strength dependence methods. The rate of the reactions with both cytochrome c and cytochrome c2 decreased rapidly with increasing ionic strength above 0.2 M NaCl. The ionic strength dependence suggested that electrostatic interactions were equally important to the reactions of the two cytochromes, even though they have opposite net charges at pH 7.0. In order to define the interaction domain on horse cytochrome c, the reaction rates of derivatives modified at single lysine amino groups with trifluoroacetyl or trifluoromethylphenylcarbamoyl were measured. Modification of lysine-8, -13, -27, -72, -79, and -87 surrounding the heme crevice was found to significantly lower the rate of the reaction, while modification of lysines in other regions had no effect. This result indicates that lysines surrounding the heme crevice of horse cytochrome c are involved in electrostatic interactions with carboxylate groups at the binding site on the cytochrome bc1 complex. In order to define the reaction domain on cytochrome c2, a fraction consisting of a mixture of singly labeled 4-carboxy-2,6-dinitrophenylcytochrome c2 derivatives modified at lysine-35, -88, -95, -97, and -105 and several unidentified lysines was prepared. Although it was not possible to resolve these derivatives, all of the identified lysines are located on the front surface of cytochrome c2 near the heme crevice. The rate of reaction of this fraction was significantly smaller than that of native cytochrome c2, suggesting that the binding domain on cytochrome c2 is also located at the heme crevice.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Evidence for multiple carboxymethylcellulase genes in Pseudomonas fluorescens subsp. cellulosa.

A genomic library of Pseudomonas fluorescens subsp. cellulosa DNA was constructed in bacteriophage lambda 47.1 and recombinants expressing carboxymethylcellulase (CMCase) activity isolated. A 7.3 kb partial EcoRI fragment, a 9.4 kb EcoRI fragment and a 5.8 kb HindIII fragment were subcloned from three different phages into pUC18 to yield recombinant plasmids pJHH1, pJHH3 and pGJH2 respectively. Cells of Escherichia coli harbouring these plasmids expressed CMCase activity. The positions of the CMCase genes in the three plasmids were determined by subcloning and transposon mutagenesis. pJHH1 contained two distinct DNA regions encoding CMCases, which were controlled by the same promoter. All four cloned enzymes cleaved p-nitrophenyl-beta-D-glucopyranoside, although at a very low rate, but none exhibited exoglucanase activity. In common with other extracellular enzymes cloned in E. coli, all the CMCases were exported to the periplasmic space in the enteric bacterium. The carboxymethylcellulase genes encoded by pJHH1 and pJHH3, were subject to glucose repression in E. coli.

Cell Compartmentation↗
PubMed1987

Ethanol effects on aggression of rats selected for different levels of aggressiveness.

Male rats confronting strange male intruders into their home cages were divided into nonaggressive, low-to-intermediate aggressive, and highly aggressive groups. In tests with low (0.3 and 0.6 g/kg) doses of ethanol the nonaggressive rats did not become aggressive; low-intermediate animals showed a significant increase in frequency and duration of attack behaviors; but highly aggressive rats displayed a slight (nonsignificant) decline. A higher ethanol dose (1.2 g/kg) consistently led to decreased aggression. This rate-dependency of the enhancement of aggression by low doses of ethanol is concordant with a view that the mechanism of this enhancement involves ethanol interference with some mechanism which normally acts to limit or inhibit attack.

Aggression↗
PubMed1987

Ethanol effects on female aggression vary with opponent size and time within session.

Female rats displayed different patterns of attack to large and small male intruders into their home cages, as a function of ethanol dose levels. In confrontations with small male intruders, female attack increased significantly at 0.3 g/kg ethanol, declining to saline levels with higher doses (0.6 and 1.2 g/kg). Attack toward large intruders was (nonsignificantly) higher at 0.3 g/kg ethanol, and declined to significantly lower than saline levels with the higher ethanol doses. The attack increases seen with low ethanol doses came in the initial 5-min block of the 30 min test session, and did not persist. These findings suggest that low ethanol doses may especially increase overt aggression in situations in which the tendency to attack is only moderately inhibited by factors such as opponent size or the potential danger of retaliatory attack.

Aggression↗
PubMed1987

Chemical mutagenesis of human interferon-beta: construction, expression in E. coli, and biological activity of sodium bisulfite-induced mutations.

A series of modified human interferon-beta (IFN-beta) genes was produced by sodium bisulfite treatment of the IFN-beta gene cloned in M13. A library of mutated sequences was generated from which subgenomic fragments containing one or a small number of coding alterations were isolated and substituted into the IFN-beta gene in an E. coli expression vector. A number of modified genes and their expression products were evaluated. In several instances levels of expression and biological activity profiles are altered compared to the parental gene product. A number of key amino acids can be identified, whose substitutions have marked effects on biological activity of IFN-beta.

Amino Acid Sequence↗
PubMed1987

Measurement of outcomes of general practice: comparison of three health status measures.

The broad range of medical problems seen in general practice means that the assessment of health outcomes shares much with the assessment of health status in the general community. The last two decades have seen considerable progress in health status measurement for this purpose. This paper reports the use of three such measures in a general practice setting. The 'Rand health insurance study battery', the 'sickness impact profile' and the 'general health questionnaire' were tested in two general practices in Sydney, Australia, to determine patient compliance, to assess the range of scores and discriminative ability of the instruments, and to compare the different instruments. There was a high degree of acceptance of the questionnaires, showing that patients visiting their general practitioners are prepared to complete such questionnaires. The range of scores obtained was less skewed for the Rand measures than for the sickness impact profile or the general health questionnaire, suggesting that the Rand measures should be the preferred general health status measure.

Australia↗
PubMed1987

Chlamydia trachomatis (L2 serovar) can be bound, ingested and destroyed by differentiated but not by undifferentiated human promyelocyte cell line HL-60.

As a model system for analysing interactions between chlamydiae and myeloid cells and their precursors, we have studied binding, ingestion and destruction of Chlamydia trachomatis (L2 serovar) by the human promyelocytic cell line HL-60. HL-60 cells were induced by phorbol myristate acetate (PMA) and dimethyl sulphoxide (DMSO) to differentiate along either the macrophage or the granulocyte pathway, respectively. Using an immunofluorescence assay and electron microscopy, we have shown that induced (differentiated) HL-60 cells, but not uninduced (undifferentiated) HL-60 or other cell lines treated with PMA or DMSO, exhibit increased binding, ingestion and elimination of C. trachomatis; these activities are associated with specific histochemical and antigenic markers of myeloid differentiation. These results suggest that myeloid cells acquire the ability to interact with and kill chlamydiae during cell development.

Cell Differentiation↗
PubMed1987

Diaphragmatic muscle fiber type development in swine.

Diaphragmatic muscle fiber types were determined in the costal and crural segments of swine diaphragm at 4 postnatal ages (1 day, 1 month, 6 months, and between 3-6 yr of age). Fiber types were differentiated by enzyme histochemistry for adenosine triphosphatase and reduced nicotinamide adenine dinucleotide. A progressive increase in the number of type I fibers occurred in both costal and crural segments from birth to 6 months of age. The number of type IIA fibers decreased and type IIB fibers increased over the same time period. Type IIC fibers were present through 1 month of age, were rarely observed at 6 months, and were not found in older animals. Type I fibers were more numerous in the crural portion of the diaphragm. The cross-sectional area of all fiber types in both costal and crural segments increased significantly with age. No preferential fiber type growth was noted in either segment of the diaphragm. These data suggest that the pig diaphragmatic muscle is differentiated into its adult form by 6 months of postnatal age, but fiber cross-sectional area growth continues along with body growth.

Adenosine Triphosphatases↗
PubMed1987

Skin absorption and cutaneous first pass metabolism of topical steroids: in vitro studies with mouse skin in organ culture.

Using mouse skin maintained in a permeability chamber-organ culture system, we have examined the percutaneous penetration and cutaneous fate of some selected steroids. At 16 hr after in vitro topical application (10 micrograms/2 cm2), the extent of permeation of the selected steroids was testosterone (65.13%) much greater than cortisol (18.1%) = estradiol (18.0%) greater than estrone (10.58%) much greater than estriol (2.45%). Permeation was accompanied by cutaneous first pass metabolism. In addition to water-soluble metabolites, other metabolites found in the perfusion medium from topical testosterone included 5 alpha-dihydrotestosterone, 5 alpha-androstanedione and androstenedione. Cortisone was identified as one of the metabolites of topical cortisol. For the estrogens, estradiol and estriol were metabolites of topical estrone, whereas estrone and estriol were metabolites of topical estradiol. The extent of cutaneous first pass metabolism of these selected steroids varies considerably. Estrone was metabolized extensively, but only limited metabolism of estradiol and cortisol was observed during their translocation through the skin. With testosterone, it was evident that an increase in the topically applied dose was accompanied by a decrease in the relative extent of both permeation and cutaneous first pass metabolism. However, cutaneous first pass metabolism of estriol was essentially negligible. These observations demonstrated that both diffusional and metabolic processes are important in the percutaneous fate of topical steroids. They also suggest that in future studies concerned with the absorption and bioavailability of topically applied chemicals, an assessment of the drug-metabolizing capabilities of the skin needs to be considered.

Administration, Cutaneous↗
PubMed1987

Lets be friends.

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Attitude of Health Personnel↗
PubMed1986

Complementation of sensitivity to alkylating agents in Escherichia coli and Chinese hamster ovary cells by expression of a cloned bacterial DNA repair gene.

Dual expression vectors derived from pSV2gpt and encoding all or part of the Escherichia coli ada+ gene have been constructed. Following transformation into an E. coli ada strain or transfection and stable integration into the genome of Chinese hamster ovary (CHO) cells, plasmid vectors containing the whole ada+ gene conferred resistance to both killing and mutagenesis by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). Thus, the bacterial DNA repair gene was functionally expressed in the mammalian cells. Plasmids containing an N-terminal fragment of the ada+ gene which encoded only one of the two methyltransferase activities of the Ada protein did not significantly protect E. coli or CHO cells against MNNG. These results are consistent with the central role of the intact ada+ gene in controlling the adaptive response to alkylating agents in E. coli. However, the data further suggest that some alkylation lesions in DNA, such as O6-methylguanine, may exert partly different biological effects in E. coli and mammalian cells.

Animals↗
PubMed1986

Induction of digitoxigenin monodigitoxoside UDP-glucuronosyltransferase activity by glucocorticoids and other inducers of cytochrome P-450p in primary monolayer cultures of adult rat hepatocytes and in human liver.

We have recently proposed that glucocorticoids induce cytochrome P-450p, a liver microsomal hemoprotein originally isolated from rats treated with the antiglucocorticoid pregnenolone 16 alpha-carbonitrile (PCN), through a mechanism that involves a stereospecific recognition system clearly distinguishable from the classic glucocorticoid receptor (Schuetz, E. G., Wrighton, S. A., Barwick, J. L., and Guzelian, P. S. (1984) J. Biol. Chem. 259, 1999-2012). We now report that digitoxigenin monodigitoxoside UDP-glucuronosyltransferase (DIG UDP-glucuronosyltransferase), a liver microsomal enzyme activity induced by PCN in rats, is also inducible, as is P-450p, in primary monolayer cultures of adult rat hepatocytes. DIG UDP-glucuronosyltransferase activity closely resembled reported characteristics of induction of P-450p in its time course of induction, concentration-response relationships, exclusivity of induction by steroids with glucocorticoid properties, unusual rank order of potency of glucocorticoid agonists, unusually high ED50 for induction by glucocorticoids, enhanced induction rather than inhibition by anti-glucocorticoids in the presence of glucocorticoids, and finally, induction by nonsteroidal inducers of P-450p. DIG UDP-glucuronosyltransferase activity was also readily detected in human liver microsomes and was elevated in two patients who had received inducers of P-450p. We conclude that the liver enzymes controlled by the postulated PCN recognition system include not only P-450p but also one or more UDP-glucuronosyltransferases.

Animals↗
PubMed1986

Neural analysis of temporally patterned sounds in the frog's thalamus: processing of pulse duration and pulse repetition rate.

We conducted a single unit study of auditory neurons in the central thalamic nucleus of the northern leopard frog. These cells, unlike those of the posterior thalamic nucleus (J. Comp. Physiol., 150 (1983) 333-344), were broadly tuned and sensitive to one or more temporal features (pulse duration and repetition rate) of complex sound signals. When compared with previous studies, these results suggest that temporal and spectral information may be processed separately by distinct populations of neurons within the frog's thalamus.

Acoustic Stimulation↗