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D Higgs

Publications and source records attributed to D Higgs.

At least 19 recordsLinked to original sources
PubMed2001

The chloroplast gene ycf9 encodes a photosystem II (PSII) core subunit, PsbZ, that participates in PSII supramolecular architecture.

We have characterized the biochemical nature and the function of PsbZ, the protein product of a ubiquitous open reading frame, which is known as ycf9 in Chlamydomonas and ORF 62 in tobacco, that is present in chloroplast and cyanobacterial genomes. After raising specific antibodies to PsbZ from Chlamydomonas and tobacco, we demonstrated that it is a bona fide photosystem II (PSII) subunit. PsbZ copurifies with PSII cores in Chlamydomonas as well as in tobacco. Accordingly, PSII mutants from Chlamydomonas and tobacco are deficient in PsbZ. Using psbZ-targeted gene inactivation in tobacco and Chlamydomonas, we show that this protein controls the interaction of PSII cores with the light-harvesting antenna; in particular, PSII-LHCII supercomplexes no longer could be isolated from PsbZ-deficient tobacco plants. The content of the minor chlorophyll binding protein CP26, and to a lesser extent that of CP29, also was altered substantially under most growth conditions in the tobacco mutant and in Chlamydomonas mutant cells grown under photoautotrophic conditions. These PsbZ-dependent changes in the supramolecular organization of the PSII cores with their peripheral antennas cause two distinct phenotypes in tobacco and are accompanied by considerable modifications in (1) the pattern of protein phosphorylation within PSII units, (2) the deepoxidation of xanthophylls, and (3) the kinetics and amplitude of nonphotochemical quenching. The role of PsbZ in excitation energy dissipation within PSII is discussed in light of its proximity to CP43, in agreement with the most recent structural data on PSII.

Amino Acid Sequence↗
PubMed2000

A new polymorphim (G->A) in the psizeta1 globin gene.

BACKGROUND AND OBJECTIVES: a-globin cluster polymorphisms are obtained with specific restriction enzymes (Xba I, Eco RI, Sac I, Apa I, Bgl II, etc) that can also have implications for genetic analysis. DESIGN AND AND METHODS: We studied three unrelated patients; one from Argentina, one from Spain and one from Australia but of Polish origin. Genomic DNA was digested with several different restriction enzymes and probes, amplified and sequenced with an ABI Prism 310 sequencer. RESULTS: In the three patients an abnormal 26 kb band appeared when they were studied with restriction enzyme Bgl II and z probe. A fragment of 944 bp was amplified with primers that cover from -280 to +714 bp of the recognition sequence of Bgl II enzyme (AGATCT) localized 5' from pseudogene z1. After digestion of this PCR product with Bgl II, two fragments of 714 and 280 bp were produced in normal controls, whereas in patient #1 the PCR fragment was undigested and in patients 2 and 3 both undigested and digested fragments were observed. Sequencing of the PCR fragment showed that in all three patients it was the same polymorphism (G->A) at nucleotide 153171 of the 16 p sequence found in the Bgl II recognition site that changed to AAATCT. INTERPRETATION AND CONCLUSIONS: We describe a new polymorphism in the yz1 first exon Bgl II restriction site (G->A). The polymorphism is associated in cis with haplotype -a3.7. The fragment obtained by PCR enabled us to corroborate the presence of the polymorphism quickly without having to use complicated sequencing techniques.

Adult↗
PubMed1999

Altering the 3 UTR endonucleolytic cleavage site of a Chlamydomonas chloroplast mRNA affects 3-end maturation in vitro but not in vivo.

The 3' ends of chloroplast mRNAs are produced by the processing of longer precursors. The 3' ends of most plastid mRNAs are located at, or several nucleotides downstream of, stem-loop structures, which act as 3'-end-processing signals and RNA stability elements. In chloroplasts of the green alga Chlamydomonas reinhardtii, 3'-end maturation of atpB mRNA involves endonucleolytic cleavage of the pre-mRNA at an AU-rich site located about 10 nucleotides downstream of the stem-loop structure. This cleavage is followed by exonucleolytic resection to generate the mature 3' end. In order to define critical nucleotides of the endonucleolytic cleavage site, we mutated its sequence. Incubation of synthetic atpB pre-RNAs containing these mutations in a chloroplast protein extract resulted in the accumulation of 3'-end-processed products. However, in two cases where the AU-rich sequence of this site was replaced with a GC-rich one, the 3' end of the stable processing product differed from that of the wild-type product. To examine whether these mutations affected atpB mRNA processing or accumulation in vivo, the endogenous 3' UTR was replaced with mutated sequences by biolistic transformation of Chlamydomonas chloroplasts. Analysis of the resulting strains revealed that the accumulation of atpB mRNA was approximately equal to that of wild-type cells, and that a wild-type atpB 3' end was generated. These results imply that Chlamydomonas atpB 3' processing parallels the situation with other endonucleases such as Escherichia coli RNAse E, where specific sequences are required for correct in vitro processing, but in vivo these mutations can be overcome.

3' Untranslated Regions↗
PubMed1997

Pulse oximetry in a cohort study of sickle cell disease.

Oxygen saturation was determined by pulse oximetry in a representative sample of Jamaican patients with steady-state sickle cell disease in a cohort study from birth. There were 220 with homozygous sickle cell (SS) disease and 142 with sickle cell-haemoglobin C (SC) disease aged 9-18 years, and 122 with a normal haemoglobin (AA) genotype aged 15-18 years. Pulse oximetry (SpO2) values were lower in SS disease (mean [95% confidence interval], 92.5 [92.0-93.0]) than in SC disease (96.7[96.5-96.9]) or AA controls (97.1 [96.8-97.3]). Inhalation of 100% oxygen in SS patients with O2 saturations below 90% consistently increased saturation to 99-100%. In SS disease, SpO2 correlated positively with haemoglobin and fetal haemoglobin and negatively with reticulocyte counts but not with MCHC, MCV or bilirubin level. Mean SpO2 in SS subjects with a normal alpha globin gene complement (mean [SD], 91.7 [3.9]%) was lower than in heterozygotes (93.4 [4.0]%) or homozygotes (96.1 [3.0]%) for alpha+ thalassaemia, the effects of alpha-thalassaemia not being explained by differences in haemoglobin or MCHC. In SS disease, SpO2 levels were not associated with age (within this age range), sex, number of sick clinic visits or number of hospital admissions. Higher SpO2 levels were associated with greater height and weight, more frequent painful crises and less frequent acute chest syndrome, but these associations were not significant after adjustment for haemoglobin level. Desaturation is common in steady-state SS disease and knowledge of the individual's steady-state value may be important in the interpreting low values during acute complications.

Adolescent↗
PubMed1996

Determinants of haemoglobin level in steady-state homozygous sickle cell disease.

High total haemoglobin levels in homozygous sickle cell (SS) disease are a risk factor for painful crises, avascular necrosis of the femoral head, proliferative sickle retinopathy, and the acute chest syndrome. Since lowering the haemoglobin level may ameliorate these features, understanding the determinants of total haemoglobin may be of practical importance. A range of possible determinants including red cell characteristics, reticulocytes, serum iron, transferrin saturation, serum ferritin, alpha thalassaemia status, red cell mass and plasma volume, oxygen affinity, red cell survival, transferrin receptor and erythropoietin levels have been measured in 62 patients selected to provide a range of total haemoglobin and fetal haemoglobin levels. There were weak negative associations of haemoglobin with mean cell volume and mean cell haemoglobin concentration, strong negative associations with proportional reticulocyte counts, oxygen affinity, plasma volume, serum transferrin receptors, and erythropoietin levels and strong positive associations with red cell mass. Weighted analysis suggested that the statistically independent determinants of haemoglobin level were alpha thalassaemia, sex, red cell mass/body weight, plasma volume/body weight, fetal haemoglobin, and red cell count. The apparent contributions of red cell survival, P50, reticulocyte count, serum transferrin receptor and erythropoietin levels were explained by the effects of these other variables. The independent determinants as a group explained 91% of the variation in haemoglobin level.

Adult↗
PubMed1996

Factors affecting prepubertal growth in homozygous sickle cell disease.

OBJECTIVE: To investigate the role of haematological indices, socioeconomic status, and morbidity in prepubertal growth in homozygous sickle cell (SS) disease. METHOD: Height, weight, and haematology were serially recorded in a cohort study of 315 children with SS disease from birth to 9 years at the sickle cell clinic of the University Hospital of the West Indies, Kingston, Jamaica. RESULTS: Height increment between 3 and 9 years correlated positively with total haemoglobin at age 7 years in boys but not girls. Attained height and weight at age 7 years correlated positively with haemoglobin and fetal haemoglobin in boys but not girls. Only the correlation between haemoglobin and weight showed a significant gender difference. Partial correlation analysis suggested that the effect of haemoglobin was accounted for by the effect of fetal haemolglobin and further analysis indicated that height correlated with F reticulocyte count (a measure of fetal haemoglobin production) in both sexes but not with the ratio of F cells to F reticulocytes (a measure of F cell enrichment). Growth was not significantly related to mean red cell volume, proportional reticulocyte count, alpha thalassaemia, socioeconomic status, or morbidity. CONCLUSION: A high concentration of fetal haemoglobin in boys with SS disease is associated with greater linear growth. It is postulated that in boys, low concentrations of fetal haemoglobin increase haemolysis and hence metabolic requirements for erythropoiesis, putting them at greater risk of poor growth. Differences in the relationship of haematology and growth between boys and girls with SS disease dictate that future analyses of growth take gender into account.

Anemia, Sickle Cell↗
PubMed1996

Ontogeny of visual and mechanosensory structure and function in Atlantic menhaden Brevoortia tyrannus

The importance of visual, mechanoreceptive and auditory inputs to escape responses was examined in larvae of the Atlantic menhaden (Brevoortia tyrannus) presented with a simulated predatory stimulus. Ontogenetic changes in the retina, superficial neuromasts and auditory bullae were examined in concert with behavioral trials in which sensory inputs were selectively blocked. Menhaden larvae showed a decrease in cone photoreceptor density and first developed rod photoreceptors when their total length (TL) reached 8­10 mm; they began summing photoreceptive inputs at 12­14 mm TL. Inflation of the auditory bullae was complete by 15 mm TL. The proliferation of superficial neuromasts varied depending on their location, with cephalic superficial neuromasts decreasing in number beginning at 19 mm TL and numbers of trunk neuromasts continuing to increase throughout the larval period. In behavioral trials, responsiveness and the reactive distance to the approaching probe increased with increasing larva total length when all sensory inputs were available (control larvae). When visual inputs were blocked, responsiveness was lower than in control larvae, but still increased ontogenetically, while reactive distance showed no difference between control larvae and those lacking visual information. When neuromasts were ablated, ontogenetic increases in responsiveness and reactive distance were absent. Inflation of the auditory bullae had no discernible effect on behavior. The anatomical and behavioral results suggest that both vision and mechanoreception are used to trigger a response to a looming predatory stimulus and that mechanoreception, but not vision, contributes to the timing of the response. Ontogenetic improvements in performance are attributed mainly to neuromast proliferation and not to ontogenetic changes in the retina.

Journal Article↗
PubMed1994

Helix pomatia agglutinin binding is a useful prognostic indicator in colorectal carcinoma.

BACKGROUND: Most deaths from colorectal carcinoma are due to metastases. A relatively reliable prognostic indicator at surgery to date is the Dukes' stage, but this is a morphologic approach that does not elucidate biochemical changes to explain why cells became metastatic. The binding sites for the lectin from the Roman snail Helix pomatia (HPA) were shown to be good prognostic indicators in breast and gastric cancer, and accordingly, this study was performed to evaluate the use of HPA binding sites as prognostic markers in colorectal carcinoma. METHODS: The histochemically detected expression of HPA binding sites in colorectal carcinomas (n = 130) was increased. The results of the histochemical findings were correlated with patient survival and tumor recurrence. RESULTS: The results indicated that the prognosis for the groups of patients whose colorectal cancer cells binded to HPA in tissue sections was almost as bad as those with Dukes' Stage C disease. CONCLUSION: Because HPA binds to N-acetylgalactosamine, the authors' results indicate that this sugar residue is at least partly involved in the process of human colorectal carcinoma cells metastasizing to regional lymph nodes and possibly also to distant sites.

Acetylgalactosamine↗
PubMed1993

The regulation of human globin gene expression.

The haemopoietic system provides a well-characterized and accessible system for studying the mechanisms of developmental regulation and differentiation in higher eukaryotes. Our current understanding of the steps involved in the early stages of differentiation are poorly understood but a great deal is now known about the mechanisms by which globin expression is regulated in cells committed to the erythroid lineage. Many of the critical cis-acting sequences and some of the important trans-acting factors involved have been identified and current work is focusing on how these interact to produce high levels of tissue-specific and developmentally regulated expression of the human globin genes.

Animals↗
PubMed1993

Transcriptional activation of human zeta 2 globin promoter by the alpha globin regulatory element (HS-40): functional role of specific nuclear factor-DNA complexes.

We studied the functional interaction between human embryonic zeta 2 globin promoter and the alpha globin regulatory element (HS-40) located 40 kb upstream of the zeta 2 globin gene. It was shown by transient expression assay that HS-40 behaved as an authentic enhancer for high-level zeta 2 globin promoter activity in K562 cells, an erythroid cell line of embryonic and/or fetal origin. Although sequences located between -559 and -88 of the zeta 2 globin gene were dispensable for its expression on enhancerless plasmids, they were required for the HS-40 enhancer-mediated activity of the zeta 2 globin promoter. Site-directed mutagenesis demonstrated that this HS-40 enhancer-zeta 2 globin promoter interaction is mediated by the two GATA-1 factor binding motifs located at -230 and -104, respectively. The functional domains of HS-40 were also mapped. Bal 31 deletion mapping data suggested that one GATA-1 motif, one GT motif, and two NF-E2/AP1 motifs together formed the functional core of HS-40 in the erythroid-specific activation of the zeta 2 globin promoter. Site-directed mutagenesis further demonstrated that the enhancer function of one of the two NF-E2/AP1 motifs of HS-40 is mediated through its binding to NF-E2 but not AP1 transcription factor. Finally, we did genomic footprinting of the HS-40 enhancer region in K562 cells, adult nucleated erythroblasts, and different nonerythroid cells. All sequence motifs within the functional core of HS-40, as mapped by transient expression analysis, appeared to bind a nuclear factor(s) in living K562 cells but not in nonerythroid cells. On the other hand, only one of the apparently nonfunctional sequence motifs was bound with factors in vivo. In comparison to K562, nucleated erythroblasts from adult human bone marrow exhibited a similar but nonidentical pattern of nuclear factor binding in vivo at the HS-40 region. These data suggest that transcriptional activation of human embryonic zeta 2 globin gene and the fetal/adult alpha globin genes is mediated by erythroid cell-specific and developmental stage-specific nuclear factor-DNA complexes which form at the enhancer (HS-40) and the globin promoters.

Base Sequence↗
PubMed1991

Knowledge and beliefs about cancer in a socioeconomically disadvantaged population.

Americans living in poverty experience a higher incidence of and greater mortality from cancer than the nonpoor. At least 50% of the difference in mortality is believed to be due to delay in diagnosis, although risk-promoting lifestyles and behaviors also contribute to decreased survival. A potential exacerbating factor among the poor is inadequate information and knowledge about cancer and its treatment. Interviews were conducted with 128 cancer patients from a socioeconomically disadvantaged population to assess knowledge of cancer and its treatment and to evaluate care-seeking behaviors. Results indicated that although patients relied primarily on their physicians for information about their disease and treatment, a number of misconceptions regarding cancer existed in this population. Notably, nearly 50% of the patients surveyed either denied or did not know that smoking was related to the development of cancer. Additionally, patients frequently reported inappropriate care-seeking behaviors when asked to respond to a series of common disease-related signs or symptoms. These findings suggest that misinformation and misconceptions regarding cancer and its treatment among patients in this sample may contribute to inappropriate care-seeking behaviors.

Consumer Behavior↗
PubMed1991

The haematology of homozygous sickle cell disease after the age of 40 years.

Haematological indices have been studied in 181 patients with homozygous sickle cell (SS) disease aged 40-73 years. Cross-sectional analyses in 5-year age bands indicated age-related decreases in HbF (males only), total haemoglobin and platelet counts. Longitudinal studies within individuals confirmed the downward age-related trend in haemoglobin and platelets and also revealed a falling reticulocyte count, most significant when expressed as absolute values. Total nucleated cells also fell although the decline was significant only in females. These observations are consistent with a progressive bone marrow failure which is not explained by the commonly occurring renal impairment in older SS patients since the changes persisted in analyses confined to patients with normal creatinine levels. The mechanism of this bone marrow failure is currently unknown.

Adult↗
PubMed1991

The red cell distribution width in sickle cell disease--is it of clinical value?

The red cell distribution width (RDW) has been studied during the clinical steady state in 1121 patients with homozygous sickle cell (SS) disease, 344 with sickle cell-haemoglobin C (SC) disease, 68 with sickle cell-beta+ thalassaemia, 49 with sickle cell beta 0 thalassaemia and in 130 control subjects with a normal (AA) genotype. The mean RDW was moderately increased in S beta + thalassaemia and SC disease and markedly increased in S beta 0 thalassaemia and SS disease. In SS, SC and S beta 0 thalassaemia genotypes, lower RDW values occurred in females and with alpha thalassaemia. The RDW correlated negatively with total haemoglobin, mean cell haemoglobin concentration, mean cell volume, and fetal haemoglobin (HbF) and positively with reticulocyte count in SS disease. A low RDW was associated with higher weight and less frequent dactylitis, painful crisis, acute chest syndrome, acute splenic sequestration, and hospital admissions. A low RDW in SS disease is consistent with a high total haemoglobin, high HbF, low reticulocyte count, alpha thalassaemia, and a more mild clinical course.

Adolescent↗
PubMed1989

Ifosfamide: a clinical review.

Although ifosfamide first underwent clinical trials 15 years ago, it has largely been ignored by the American oncology community until the last few years. Earlier concerns about dose-limiting hemorrhagic cystitis have been mitigated by the development of effective urothelial protectors such as mesna. Furthermore, ifosfamide is not completely cross-resistant with cyclophosphamide. Ifosfamide has activity in a variety of disseminated refractory solid tumors that do not traditionally respond to conventional alkylating agent therapy, specifically refractory germ cell tumors, soft tissue sarcomas, and malignant lymphomas. The decreased myelosuppression and lack of apparent cross-resistance compared with cyclophosphamide make ifosfamide an ideal drug for inclusion in combination chemotherapy. While clarification of the differences between ifosfamide and cyclophosphamide is ongoing, ifosfamide may eventually replace cyclophosphamide in conventional combination chemotherapy regimens for a variety of solid tumors. At present, it has clear-cut major activity in refractory germ cell tumors and has become an integral component of a curative salvage regimen.

Antineoplastic Agents↗