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J Garrett

Publications and source records attributed to J Garrett.

At least 73 records · Page 4Linked to original sources
PubMed1986

The amino terminus of the yeast F1-ATPase beta-subunit precursor functions as a mitochondrial import signal.

The ATP2 gene of Saccharomyces cerevisiae codes for the cytoplasmically synthesized beta-subunit protein of the mitochondrial F1-ATPase. To define the amino acid sequence determinants necessary for the in vivo targeting and import of this protein into mitochondria, we have constructed gene fusions between the ATP2 gene and either the Escherichia coli lacZ gene or the S. cerevisiae SUC2 gene (which codes for invertase). The ATP2-lacZ and ATP2-SUC2 gene fusions code for hybrid proteins that are efficiently targeted to yeast mitochondria in vivo. The mitochondrially associated hybrid proteins fractionate with the inner mitochondrial membrane and are resistant to proteinase digestion in the isolated organelle. Results obtained with the gene fusions and with targeting-defective ATP2 deletion mutants provide evidence that the amino-terminal 27 amino acids of the beta-subunit protein precursor are sufficient to direct both specific sorting of this protein to yeast mitochondria and its import into the organelle. Also, we have observed that certain of the mitochondrially associated Atp2-LacZ and Atp2-Suc2 hybrid proteins confer a novel respiration-defective phenotype to yeast cells.

Amino Acid Sequence↗
PubMed1986

Mutational analysis of bacteriophage lambda lysis gene S.

A plasmid carrying the bacteriophage lambda lysis genes under lac control was subjected to hydroxylamine mutagenesis, and mutations eliminating the host lethality of the S gene were selected. DNA sequence analysis revealed 48 single-base mutations which resulted in alterations within the coding sequence of the S gene. Thirty-three different missense alleles were generated. Most of the missense changes clustered in the first two-thirds of the molecule from the N terminus. A simple model for the disposition of the S protein within the inner membrane can be derived from inspection of the primary sequence. In the first 60 residues, there are two distinct stretches of predominantly hydrophobic amino acids, each region having a net neutral charge and extending for at least 20 residues. These regions resemble canonical membrane-spanning domains. In the model, the two domains span the bilayer as a pair of net neutral charge helices, and the N-terminal 10 to 12 residues extend into the periplasm. The mutational pattern is largely consistent with the model. Charge changes within the putative imbedded regions render the protein nonfunctional. Loss of glycine residues at crucial reverse-turn domains which would be required to reorient the molecule to reenter the membrane also inactivate the molecule. Finally, a number of neutral and rather subtle mutations such as Ala to Val and Met to Ile are found, mostly within the putative spanning regions. Although no obvious explanation exists for this subtle and heterogeneous class of mutations, it is noted that all of the changes result in a loss of alpha-helical character as predicted by Chou-Fasman theoretical analysis. Alternative explanations for some of these changes are also possible, including a reduction in net translation rate due to substitution of a rare codon for a common one. The model and the pattern of mutations have implications for the probable oligomerization of the S protein at the time of endolysin release at the end of the vegetative growth period.

Alleles↗
PubMed1986

Postsynaptic alpha-adrenoceptor subtypes in the internal carotid, mesenteric, splenic, renal and femoral vascular beds of the dog.

Pressor effects of noradrenaline, phenylephrine and alpha-methylnoradrenaline and the inhibition of these effects by prazosin or yohimbine (or both) were studied in vivo in the renal, splenic, femoral, anterior mesenteric and internal carotid vascular beds of the dog. In all the vascular beds noradrenaline was more potent than alpha-methylnoradrenaline and alpha-methylnoradrenaline was more potent than phenylephrine. However, the ratios between the ED50 for phenylephrine and the ED50 for alpha-methylnoradrenaline in the mesenteric, in the femoral, in the splenic and in the renal circulations was 2.19, 1.89, 1.48, and 1.33, respectively, showing that the relative potency of phenylephrine increased in that order. In the internal carotid vascular bed it was not possible to determine any value. Furthermore, in the renal vascular bed, prazosin (100 micrograms/kg) inhibited pressor responses to all agonists more readily than yohimbine (250 micrograms/kg) and yohimbine was more potent than prazosin against all the agonists in the mesenteric and in the femoral vascular beds. Our results show that: there are both postsynaptic alpha 1- and alpha 2-adrenoceptors in the four vascular beds; the contribution of alpha 2-adrenoceptors to pressor responses to sympathomimetic agents is maximal in the mesenteric followed by the femoral, the splenic and the renal vascular bed, whereas the participation of alpha 1-adrenoceptors is maximal in the renal and progressively smaller in the splenic, in the femoral and in the mesenteric vascular bed, where it reaches the lowest value.

Animals↗
PubMed1985

Effects of trifluoperazine on platelet activation.

Previous reports of the inhibitory effects of trifluoperazine on platelet responses to different aggregating agents have been conflicting, and the mechanism of action remains unclear. We have found that aggregation by minimum concentrations of collagen and arachidonic acid, and second phase aggregation by minimum concentrations of ADP, thrombin, epinephrine and the calcium ionophore A23187 were inhibited by 40-60 microM trifluoperazine. The first phase of aggregation by a minimum concentration of epinephrine was completely inhibited by 100 microM trifluoperazine, and the first phase of aggregation induced by ADP, thrombin or A23187 was decreased by 300 microM trifluoperazine. The platelet shape change caused by collagen, but by no other aggregating agent examined, was inhibited by 300 microM trifluoperazine. Secretion of 3H-5 hydroxytryptamine by minimum concentrations of ADP, collagen, epinephrine and arachidonic acid was completely suppressed by 50 microM trifluoperazine. Secretion by thrombin and A23187 was incompletely inhibited by 300 microM trifluoperazine. Thromboxane B2 formation caused by all aggregating agents, except epinephrine, was incompletely suppressed by 50 microM trifluoperazine, and 300 microM trifluoperazine only caused complete inhibition of thromboxane B2 formation by ADP, collagen and epinephrine. The phorbol ester, TPA, which mimics diacylglycerol by activating protein kinase C, caused aggregation and secretion. Aggregation, but not secretion, by low concentrations of TPA was inhibited by concentrations of trifluoperazine as low as 50 microM. However, aggregation by a combination of TPA and A23187 was only inhibited by concentrations of trifluoperazine in excess of 100 microM. Secretion by TPA was inhibited by concentrations of trifluoperazine in excess of 200 microM. Our findings suggest that low concentrations of trifluoperazine inhibit platelet activation by inhibiting phospholipase A2, and that higher concentrations inhibit platelet responses by interfering with protein kinase C.

Adenosine Diphosphate↗
PubMed1985

Adrenaline activates in the intact dog a positive feedback loop causing an increase in noradrenaline plasma levels.

Intravenous adrenaline infusions (100 ng . kg-1 min-1) during 30 min resulted in an increase in dog plasma adrenaline and caused a very marked increase in noradrenaline, beginning at 15 min of the infusion and reaching a maximum (10-fold increase) at the end of the infusion. The heart, but not the vascular tissue, showed an increase in adrenaline content. Propranolol (0.5 + 0.5 mg . kg-1) or cocaine (0.5 + 0.5 mg . kg-1) prevented the increase in plasma noradrenaline caused by adrenaline. Isoprenaline (10 ng . kg-1 . min-1) infused during 30 min caused a smaller (2.7-fold) increase in noradrenaline levels, and those effects were also prevented by propranolol or cocaine. From these results, it is concluded that in vivo the increase in noradrenaline plasma levels is due to an activation of beta-adrenoceptors and that this plasma noradrenaline appears to be of neuronal origin. The results also suggest that adrenaline or isoprenaline, after being taken up into nerve terminals, when released activate presynaptic beta-receptors and facilitate the release of neuronal noradrenaline.

Animals↗
PubMed1984

Platelet activation by circulating levels of hormones: a possible link in coronary heart disease.

Blood platelets participating in the formation of haemostatic plugs or thrombi are likely to be exposed to combinations of several agonists. We have found that platelet aggregation and the release reaction are enhanced by combinations of the hormones adrenaline, noradrenaline, vasopressin and 5 hydroxytryptamine acting synergistically at levels obtained in circulating blood for three of these hormones. If surges of adrenaline and other hormones sensitize platelets this may provide a link between some of the risk factors and coronary heart disease.

Adult↗
PubMed1984

Improved control of bulky prostate carcinoma with sequential estrogen and radiation therapy.

Patients with bulky prostate cancer have usually been treated by palliative measures because the likelihood of tumor control with definitive irradiation has been low and the development of distant metastases high. The addition of estrogen to irradiation has not been shown to be of value. However, we believe the method of estrogen administration may have been the cause for the apparent lack of benefit. Estrogen had been started either concurrent with irradiation or had been used for palliation and was given for long and unscheduled time periods prior to irradiation. We have used estrogen for two months prior to and concurrent with irradiation. We postulated that in those patients with estrogen responsive cancer, the reduced tumor burden prior to irradiation could enhance tumor control and survival. Between 1975 and 1980, 25 patients with bulky prostate cancer received sequential estrogen and irradiation, 12 patients irradiation alone and six patients irradiation after having become refractory to long-term estrogen use. One patient was lost to follow-up. Eighteen of 25 (72%) treated by sequential estrogen and irradiation, 14/17 (82%) with estrogen responsive cancer and 4/8 (50%) with estrogen resistant cancer had a complete tumor response. Six of 11 (55%) patients treated by irradiation alone and 2/6 (33%) treated by irradiation for estrogen refractory cancer had a complete tumor response. Disease-free survival was observed in 13/25 (52%) treated by sequential estrogen and irradiation, and 8/17 patients (47%) with irradiation. It is also possible the improved survival in the estrogen responsive group was a direct result of improved local control. Persistent local disease can act as a source for distant metastases. Distant metastases was observed in 15% of patients when the primary tumor was controlled and 30% when there was persistent or recurrent local disease. Also, progressive local disease can be an important cause of death. This was most evident in our patients with estrogen refractory cancer. Almost all patients in this group had progressive local disease that caused serious urinary bleeding and urinary infection that were considered the major cause of death. Our results suggest bulky prostate cancer should be aggressively treated when first diagnosed. The value of adjunct estrogen is unproven. Our results with the use of estrogen prior to and concurrent with irradiation is encouraging. Estrogen may shrink the cancer and allow for a more favorable geometry for external irradiation. Tumor control and survival may be thereby improved.(ABSTRACT TRUNCATED AT 400 WORDS)

Aged↗
PubMed1983

Aetiology of chronic constrictive pericarditis.

In a consecutive series of 32 cases of chronic constrictive pericarditis treated by pericardiectomy during the past 25 years, four were attributable to rheumatoid disease, two to trauma, one to sarcoidosis, and four, at a maximum, to tuberculosis. In the remaining 21 cases of undetermined aetiology there was no evidence of tuberculosis. It appears, therefore, that tuberculosis was not a common cause of chronic constrictive pericarditis during the period under review, which included the 1950s and early 1960s when tuberculosis was widespread.

Adolescent↗
PubMed1981

Cell lysis by induction of cloned lambda lysis genes.

The lysis gene region of bacteriophage lambda, including genes S, R, and Rz, was cloned into the plasmid pBH20. In the recombinant plasmid, the lysis genes are expressed under the control of the lacOP region. Induction of this "lysis operon" with the lac inducer, IPTG, under conditions where transcription from the lacOP region is not subject to catabolite repression, results in a sharply defined lysis after 35 min. Premature lysis can be accomplished by cyanide, chloramphenicol, or chloroform, exactly as in bacteriophage lambda infected cells. The lysis gene region of an S- mutant was also cloned into pBH20. Induction of the S- lysis operon has no apparent effect on culture growth; however, large quantities of bacteriolytic activity accumulate intracellularly. Neither cyanide nor chloramphenicol causes lysis in the induced S- clones. Thus premature lysis appears to be entirely an S-dependent phenomenon. A model for the control of lysis in bacteriophage lambda infections is presented in which it is the accumulation of the S gene product in competition with a host "anti-S" protein that determines lysis timing.

Bacteriophage lambda↗