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M Reyes

Publications and source records attributed to M Reyes.

At least 73 records · Page 4Linked to original sources
PubMed1994

New 2-hydroxy fatty acids in the Caribbean urchin Tripneustes esculentus.

The novel alpha-hydroxy fatty acids 2-hydroxy-13-docosenoic acid [1a], 2-hydroxy-14-tricosenoic acid [2a], and 2-hydroxy-15-tetracosenoic acid [3a] were identified in the Caribbean urchin, Tripneustes esculentus. The double-bond positions of the novel alpha-hydroxy fatty acids were determined by derivatization with dimethyl disulfide and shown to correlate with the corresponding non-hydroxylated mono-unsaturated fatty acids, 13-docosenoic acid, 14-tricosenoic acid, and 15-tetracosenoic acid also present in T. esculentus. The total fatty acid composition of the urchins is also reported where cis-5-olefinic fatty acids such as 5,9-octadecadienoic acid and 5,11-eicosadienoic acid were found to predominate in the mixture. Cholesterol was the predominant sterol in T. esculentus.

Aldehydes↗
PubMed1993

Characterization of the structural requirements for assembly and nucleotide binding of an ATP-binding cassette transporter. The maltose transport system of Escherichia coli.

The periplasmic maltose-binding protein-dependent, maltose transport system of Escherichia coli is a well studied member of the ATP-binding cassette family of transport ATPases. In addition to the water-soluble maltose-binding protein, the system comprises three membrane proteins, MalF, MalG, and MalK, which form a heterotetrameric complex (FGK2) in the cytoplasmic membrane. The purified complex exhibits transport-associated ATPase activity. To characterize the requirements for nucleotide binding and hydrolysis by the FGK2 complex, we used plasmids to express different combinations of the individual subunits as well as mutant forms of the MalK subunit. Prior to measuring nucleotide binding, we examined membrane preparations for the presence of each subunit from strains that contained all possible permutations of the three structural genes, malF, malG, and malK. We found that when all three genes were present or when malF and malK were present together, the corresponding antigens were detected easily on Western immunoblots and were soluble in the non-ionic detergent, Triton X-100. In contrast, all other permutations resulted in decreased amounts of antigen or antigen that was Triton X-100-insoluble. We relied on photocross-linking with 8-azido-[32P]ATP and ATP hydrolysis as indicators of the ability of the transport complex to interact with purine nucleotides. 8-Azido-[32P]ATP was photocross-linked to the MalK subunit. Photolabeling of MalK was inhibited by ATP, ADP, and GTP and not by other nucleotides. Photolabeling of MalK required the presence of MalF but not MalG. Mutations in malK that affect amino acid residues thought to be directly involved in nucleotide binding did indeed abolish labeling and resulted in loss of transport activity without affecting protein stability. In general, ATP hydrolysis correlated with the photocross-linking. A notable exception is the MalK941 mutant protein which retained the ability to be labeled by 8-azido-[32P]ATP but was unable to catalyze detectable levels of ATP hydrolysis. Some, but not all, of the malK mutations were dominant to wild type. To study the mechanism of dominance we devised a means of measuring the ability of different wild-type and mutant MalK proteins to interact with the MalF and MalG subunits. This assay relies on the fact that, when a bifunctional MalK-LacZ hybrid protein is associated with the MalF and MalG subunits, it is membrane-bound. Excess MalK competed with the MalK-LacZ hybrid protein for sites in the membrane and resulted in the hybrid fractionating as a soluble protein.(ABSTRACT TRUNCATED AT 400 WORDS)

ATP-Binding Cassette Transporters↗
PubMed1992

Diagnostic accuracy of AIDS-related CNS lesions.

Because of the high incidence of neurological complications seen in patients with acquired immunodeficiency syndrome (AIDS), an increasing number of these cases are being referred to neurosurgeons for consideration of intracranial biopsy. To better determine the need for biopsy in these patients we evaluated the accuracy of non-tissue-based neurological diagnoses in AIDS patients who subsequently had a final diagnosis on the basis of biopsy or postmortem brain examinations. The records of 56 AIDS patients who had undergone either autopsy or brain biopsy were retrospectively reviewed. Of the ten patients who underwent biopsy, three were found to have a lesion that was different from the suspected diagnosis and that resulted in a change in treatment. Thirty patients with neurological symptoms had postmortem brain examinations. In the case of the 12 patients who had carried specific diagnoses and received treatments based on those diagnoses, only six diagnoses (50%) were proven correct at autopsy. Of the 18 cases that did not record a specific antemortem diagnosis, in only 5 were normal brains reported, while the others reported a variety of nonspecific or infectious findings. Twelve patients without neurological symptoms had postmortem brain examinations and only six of these (50%) had normal or slightly atrophic brains. Case reports of the others noted nonspecific findings most of which were suggestive of subacute HIV encephalitis. The poor rate of diagnostic accuracy in this series suggests that biopsy should be considered for atypical lesions or those that do not respond to empiric therapy. The use and relative sensitivities of various diagnostic studies are also discussed.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Actinic prurigo.

Explore the source record for details and available documents.

Conjunctival Diseases↗
PubMed1992

[A giant hepatic hemangioma and pregnancy].

We present a clinical case of a pregnancy with giant hepatic hemangioma. At term it presented like a consumption coagulopathy with thrombocytopenia. Maternal and fetal color Doppler was normal. The perinatal outcome was successful.

Adult↗
PubMed1991

The activities of the Escherichia coli MalK protein in maltose transport, regulation, and inducer exclusion can be separated by mutations.

The maltose regulon consists of several genes encoding proteins involved in the uptake and utilization of maltose and maltodextrins. Five proteins make up a periplasmic binding-protein-dependent active transport system. One of these proteins, MalK, contains an ATP-binding site and is thought to couple the hydrolysis of ATP to the accumulation of substrate. Beside its function in transport, MalK has two additional roles: (i) it negatively regulates mal regulon expression and (ii) it serves as the target for regulation of transport activity by enzyme IIIGlc of the phosphotransferase system. To determine whether the three functions of MalK are separable, we have isolated and characterized three classes of malK mutations. The first type (class I) exhibited constitutive mal gene expression but still allowed normal transport of maltose; the second type (class II) lacked the ability to transport maltose but retained the ability to repress the mal genes. Class I mutations were localized in the last third of the gene, at amino acids 267 (Trp to Gly) and 346 (Gly to Ser). Mutations of class II were found at the positions 137 (Gly to Ala), 140 (delta Gln Arg), and 158 (Asp to Asn). These mutations are near or within the region of MalK that exhibits extensive homology to the B site of an ATP-binding fold. In addition, site-directed mutagenesis was used to add or remove one amino acid in the A site of the ATP-binding fold. Plasmids carrying these mutations also behaved as class II mutants. The third class of malK mutations resulted in resistance to the enzyme IIIGlc-mediated inhibitory effects of alpha-methylglucoside. These mutations did not interfere with the regulatory function of MalK. One of these mutations (exchanging a serine at position 282 for leucine) is located in a short stretch of amino acids that exhibits homology to a sequence in the Escherichia coli Lac permease in which alpha-methylglucoside-resistant mutations have been found.

ATP-Binding Cassette Transporters↗
PubMed1991

Mortality among workers exposed to external ionizing radiation at a nuclear facility in Ohio.

In a cohort mortality study of white men employed by the Mound Facility (1947 through 1979), observed deaths did not exceed those expected based on US death rates for the overall cohort or for the subcohort monitored for external ionizing radiation. Among the radiation-monitored subcohort, mortality for workers with cumulative radiation doses of at least 10 mSv was not significantly increased when compared with mortality for coworkers with cumulative doses of less than 10 mSv. A significant dose-response based on a Mantel-Haenszel test of trend was observed for all leukemias. However, when a death from chronic lymphatic leukemia, a type of leukemia generally not regarded as radiogenic, was removed from the analyses, the strength of the dose-response was reduced.

Cohort Studies↗
PubMed1989

[Anatomo-pathological changes in the biliary system caused by povidone iodide. Experimental study].

In this report, the possible effects of povidone iodide (PVP-I) on the biliary system are studied in an experimental study using dogs. We used 20 dogs divided in two study groups. Light microscopy and electronic scanning microscopy (SEM) were used. We demonstrated that in the tied choledochus, intermittent washings with PVP-I caused a notable injury pattern on the biliary system.

Animals↗
PubMed1988

Overproduction of MalK protein prevents expression of the Escherichia coli mal regulon.

The mal regulon of Escherichia coli comprises a large family of genes whose function is the metabolism of linear maltooligosaccharides. Five gene products are required for the active accumulation of maltodextrins as large as maltoheptaose. Two cytoplasmic gene products are necessary and sufficient for the intracellular catabolism of these sugars. Two newly discovered enzymes have the capacity to metabolize these sugars but are not essential for their catabolism in wild-type cells. A single regulatory protein, MalT, positively regulates the expression of all of these genes in response to intracellular inducers, one of which has been identified as maltotriose. In the course of studying the mechanism of the transport system, we have placed the structural gene for one of the transport proteins, MalK, under the control of the Ptrc promoter to produce large amounts of this protein. We found that although high-level expression of MalK was not detrimental to E. coli, the increased amount of MalK decreased the basal-level expression of the mal regulon and prevented induction of the mal system even in the presence of external maltooligosaccharides. Constitutive mutants in which MalT does not depend on the presence of the internal inducer(s) were unaffected by the increased levels of the MalK protein. These results are consistent with the idea that MalK protein somehow interferes with the activity of the MalT protein. Different models for the regulatory function of MalK are discussed.

Bacterial Proteins↗
PubMed1987

Mortality among plutonium and other radiation workers at a plutonium weapons facility.

Mortality among 5,413 white males who were employed for at least two years at a plutonium weapons facility was investigated to measure risks from exposures to low levels of plutonium and external radiation. When compared with US death rates, fewer deaths than expected were found for all causes of death, all cancers, and lung cancer. No bone cancer was observed. An excess of brain tumors was found for the cohort in general. Elevated rate ratios for all causes of death and all lymphopoietic neoplasms were found when employees with plutonium body burdens greater than or equal to 2 nCi were compared with those with body burdens less than 2 nCi, while accounting for age, calendar period, and induction time. Increased rate ratios were also found for esophageal, stomach, colon, and prostate cancers, and for lymphosarcomas and reticulum cell sarcomas. No elevated rate ratios were noted for bone and liver cancers. When employees with cumulative exposures greater than or equal to 1 rem were compared with those with exposures less than 1 rem, elevated rate ratios were found for myeloid leukemia, lymphosarcoma and reticulum cell sarcoma, liver neoplasms, and unspecified brain tumors. No overall dose-response relationships were found for plutonium or external radiation exposures. Standardized rate ratios increased, however, as plutonium body burden levels increased for all causes, all cancers, and digestive cancers at five years induction time. Standardized rate ratios also increased as external radiation exposure categories increased for all lymphopoietic cancers and unspecified brain tumors for a two-year induction period. With the exception of analyses of combined categories of death, and perhaps of lung cancer, confidence limits were wide, indicating limited precision. Nevertheless, these findings suggest that increased risks for several types of cancers cannot be ruled out at this time for individuals with plutonium body burdens of greater than or equal to 2 nCi. Plutonium-burdened individuals should continue to be studied in future years.

Air Pollutants, Radioactive↗
PubMed1987

Extensive prolongation of rat renal allograft survival following donor or nonspecific transfusions and concomitant immunosuppressant.

We report here a marked beneficial effect upon rat renal allograft survival transplanted across a strong histocompatibility barrier (BN----LEW) by pretransplant concomitant donor-strain blood transfusion (DST) and CsA treatment. Comparisons between recipient groups treated with pretransplant nonspecific blood (NST) and concomitant cyclosporine (CsA) or azathioprine (Aza) administration were also made. LEW recipients receiving only a BN renal allograft survived for a geometric average time of 8.9 days. Recipients receiving 1 ml of donor blood at weekly intervals, each week for three weeks prior to transplantation, demonstrated a geometric mean survival time (GMST) of 40.5 days. Recipients receiving this same regimen and concurrent CsA cover (5 mg/kg/day) starting 7 days prior to the first transfusion with discontinuation 5 days prior to transplantation showed extensive prolongation (greater than 100 days). Recipients treated with only CsA cover survived for a GMST of 34.4 days. LEW recipients receiving 1 ml of nonspecific blood at weekly intervals (DA, BUF, WKY, respectively) each week for 3 weeks prior to transplantation were prolonged to 27.7 days. Recipients treated with this same regimen while under CsA cover also demonstrated extended prolongation (greater than 100 days). Recipients receiving multiple donor blood transfusions under Aza (2 mg/kg/day) cover demonstrated lesser prolongation (22.8 days). Recipients receiving the multiple nonspecific blood protocol under Aza cover showed similar prolongation (38.6 days). Recipients treated only with Aza did not show prolonged survival (9.3 days). These differences in survival were considered significant among the 9 transplant groups as determined by ANOVA (P less than 0.001). The majority of recipient groups showed relatively poor renal function over their life spans, independent of whether prolongation occurred. Yet, renal function in the NST or particularly the DST groups covered by pretransplant CsA, demonstrated the best renal function in our laboratory over many years of investigations using the BN----LEW combination. In conclusion, there was a dramatic synergistic beneficial effect of prior multiple DST or NST specific to CsA, as opposed to another immunopharmacologic agent, Aza.

Animals↗
PubMed1986

Transport of p-nitrophenyl-alpha-maltoside by the maltose transport system of Escherichia coli and its subsequent hydrolysis by a cytoplasmic alpha-maltosidase.

In wild-type Escherichia coli the activity of the maltose transport system is dependent on a periplasmic maltose-binding protein. It has been possible, however, to isolate mutants in which transport activity is mediated by the membrane components of the system and is no longer dependent on the periplasmic binding protein. In this manuscript we show that in these binding protein-independent strains, p-nitrophenyl-alpha-maltoside is a potent inhibitor of maltose transport. In contrast, p-nitrophenyl-alpha-maltoside is only a weak inhibitor of maltose transport in wild-type bacteria. In addition, we show that p-nitrophenyl-alpha-maltoside is transported by the binding protein-independent strains but not by wild-type bacteria. We were able to detect transport of this compound because there is a cytoplasmic enzyme that cleaves p-nitrophenyl-alpha-maltoside. This enzyme has not previously been described. We show that although the synthesis of this enzyme is subject to the same regulation as the components of the maltose regulon, and is MalT dependent, it is not coded for by a known mal gene. We refer to this enzyme as alpha-maltosidase. These results strengthen our proposal that the membrane components of the maltose transport system comprise a recognition site for maltose and related substrates.

ATP-Binding Cassette Transporters↗