Transactivation and inhibitory domains of hypoxia-inducible factor 1alpha. Modulation of transcriptional activity by oxygen tension

Hypoxia-inducible factor 1 (HIF-1) binds to cis-acting hypoxia-response elements within the erythropoietin, vascular endothelial growth factor, and other genes to activate transcription in hypoxic cells. HIF-1 is a basic helix-loop-helix transcription factor composed of HIF-1alpha and HIF-1beta subunits. Here, we demonstrate that HIF-1alpha contains two transactivation domains located between amino acids 531 and 826. When expressed as GAL4 fusion proteins, the transcriptional activity of these domains increased in response to hypoxia. Fusion protein levels were unaffected by changes in cellular O2 tension. Two minimal transactivation domains were localized to amino acid residues 531-575 and 786-826. The transcriptional activation domains were separated by amino acid sequences that inhibited transactivation. Deletion analysis demonstrated that the gradual removal of inhibitory domain sequences (amino acids 576-785) was associated with progressively increased transcriptional activity of the fusion proteins, especially in cells cultured at 20% O2. Transcriptional activity of GAL4/HIF-1alpha fusion proteins was increased in cells exposed to 1% O2, cobalt chloride, or desferrioxamine, each of which also increased levels of endogenous HIF-1alpha protein but did not affect fusion protein levels. These results indicate that increased transcriptional activity mediated by HIF-1 in hypoxic cells results from both increased HIF-1alpha protein levels and increased activity of HIF-1alpha transactivation domains.

Perinatal lethality and multiple craniofacial malformations in MSX2 transgenic mice

MSX2 is a homeodomain transcription factor that has been implicated in craniofacial morphogenesis on the basis of its expression pattern during mouse development and the finding of a missense mutation (P148H) in humans affected with Boston-type craniosynostosis. We have generated transgenic mice carrying a 34 kb DNA fragment encompassing a human MSX2 gene encoding either wild-type or mutant (P148H) MSX2. Inheritance of either transgene resulted in perinatal lethality and multiple craniofacial malformations of varying severity, including mandibular hypoplasia, cleft secondary palate, exencephaly, and median facial cleft, which are among the severe craniofacial malformations observed in humans. Transgenic mice also manifested aplasia of the interparietal bone and decreased ossification of the hyoid. Transgene-induced malformations involved cranial neural-crest derivatives, were characterized by a deficiency of tissue, and were similar to malformations associated with embryonic exposure to ethanol or retinoic acid, teratogens that cause increased cell death. Together with previous observations implicating MSX2 expression in developmentally-programmed cell death, these results suggest that wild-type levels of MSX2 activity may establish a balance between survival and apoptosis of neural crest-derived cells required for proper craniofacial morphogenesis.

Structural and functional analysis of hypoxia-inducible factor 1

Hypoxia-inducible factor 1 (HIF-1) is a basic helix-loop-helix protein that activates transcription of hypoxia-inducible genes, including those encoding: erythropoietin, vascular endothelial growth factor, heme oxygenase-1, inducible nitric oxide synthase, and the glycolytic enzymes aldolase A, enolase 1, lactate dehydrogenase A, phosphofructokinase I, and phosphoglycerate kinase 1. Hypoxia response elements from these genes consist of a HIF-1 binding site (that contains the core sequence 5'-CGTG-3') as well as additional DNA sequences that are required for function, which in some elements include a second HIF-1 binding site. HIF-1 is a heterodimer. The HIF-1 alpha subunit is unique to HIF-1, whereas HIF-1 beta (ARNT) can dimerize with other bHLH-PAS proteins. Structural analysis of HIF-1 alpha revealed that dimerization with HIF-1 beta (ARNT) requires the HLH and PAS domains, DNA binding is mediated by the basic domain, and that HIF-1 alpha contains a carboxyl-terminal transactivation domain. Co-transfection of HIF-1 alpha and HIF-1 beta (ARNT) expression vectors and a reporter gene containing a wild-type hypoxia response element resulted in increased transcription in non-hypoxic cells and a superinduction of transcription in hypoxic cells, whereas HIF-1 expression vectors had no effect on the transcription of reporter genes containing a mutation in the HIF-1 binding site. HIF-1 alpha and HIF-1 beta (ARNT) protein levels were induced by hypoxia in all primary and transformed cell lines examined. In HeLa cells, the levels of HIF-1 alpha and HIF-1 beta protein and HIF-1 DNA-binding activity increased exponentially as cellular oxygen tension decreased, with maximum values at 0.5% oxygen and half-maximal values at 1.5 to 2% oxygen. HIF-1 alpha and HIF-1 beta (ARNT) mRNAs were detected in all human, mouse, and rat organs assayed and mRNA expression was modestly induced in rodents subjected to hypoxia. HIF-1 alpha protein levels were induced in vivo when animals were subjected to anemia or hypoxia. The HIF1A gene was mapped to human chromosome 14q21-q24 and mouse chromosome 12.

Dimerization, DNA binding, and transactivation properties of hypoxia-inducible factor 1

Hypoxia-inducible factor 1 (HIF-1) is a heterodimeric basic helix-loop-helix transcription factor that regulates hypoxia-inducible genes including the human erythropoietin (EPO) gene. In this study, we report structural features of the HIF-1alpha subunit that are required for heterodimerization, DNA binding, and transactivation. The HIF-1alpha and HIF-1beta (ARNT; aryl hydrocarbon receptor nuclear translocator) subunits were coimmunoprecipitated from nuclear extracts, indicating that these proteins heterodimerize in the absence of DNA. In vitro-translated HIF-1alpha and HIF-1beta generated a HIF-1/DNA complex with similar electrophoretic mobility and sequence specificity as HIF-1 present in nuclear extracts from hypoxic cells. Compared to 826-amino acid, full-length HIF-1alpha, amino acids 1-166 mediated heterodimerization with HIF-1beta (ARNT), but amino acids 1-390 were required for optimal DNA binding. A deletion involving the basic domain of HIF-1alpha eliminated DNA binding without affecting heterodimerization. In cotransfection assays, forced expression of recombinant HIF-1alpha and HIF-1beta (ARNT) activated transcription of reporter genes containing EPO enhancer sequences with intact, but not mutant, HIF-1 binding sites. Deletion of the carboxy terminus of HIF-1alpha (amino acids 391-826) markedly decreased the ability of recombinant HIF-1 to activate transcription. Overexpression of a HIF-1alpha construct with deletions of the basic domain and carboxy terminus blocked reporter gene activation by endogenous HIF-1 in hypoxic cells.

Two different glycosyltransferase defects that result in GalNAc alpha-O-peptide (Tn) expression

This study shows for the first time that different glycosyltransferase defects in the biosynthesis of O-linked oligosaccharides give rise to the same GalNAc alpha-O-Ser/Thr determinant on Tn erythrocytes and colorectal carcinoma cells. The O-linked oligosaccharides isolated from the glycophorins of Tn erythrocytes contained predominantly alpha-N-acetylgalactosamine-O-Ser/Thr (Tn antigen) and sialyl-Tn. A marked reduction in normal sialylated oligosaccharides was also observed. Monoclonal antibody BRIC 111 raised against Tn erythrocytes reacted with both Tn erythrocytes and colorectal carcinoma tissues. Weak staining was detected in the supranuclear area and at the surface membranes in normal colorectal cells, but was absent from goblet cell vesicles. An increase in supranuclear staining over controls was found in tumour tissue and in the majority of resection margin specimens. The highest levels of staining were present in transitional mucosa, adjacent to the tumours where goblet vesicles were also positive. Glycosylation defects in the same patients were further studied by determination of the activity of glycosyltransferases in mucosal tissue from control and cancer patients. The reduction in or loss of beta 1-3 N-acetylglucosaminyl transferase activity to GalNAc-peptide in asialo-ovine submaxillary gland glycoprotein was detected by direct assay and by isolation of the oligosaccharides from the incubation products. No differences in N-acetylglucosaminyl-, galactosyl- or sialyl-transfer to Gal beta 1-3GalNAc in antifreeze glycoprotein or in sialyl transferase to asialo-ovine submaxillary gland glycoprotein were detected. Our study shows that the GalNAc alpha-O-Ser/Thr determinant on Tn erythrocytes and in colorectal carcinoma results from different glycosyltransferase defects in separate biosynthetic pathways for haematopoietic and epithelial tissues.

Studies on the Mitchell Grass Association in South-Western Queensland. 3. Pasture and Wool Production Under Different Rates of Stocking and Continuous or Rotational Grazing

Pasture productivity and wool production on the Warrego Mitchell grass (Astrebla spp.) rangeland in south-westem Queensland were studied over a period of 13 years under continuous or rotational grazing, each at three stocking rates. The stocking rates were one sheep to three, two or one hectares and the rotational grazing was a six- monthly system of summer or winter grazing. The grazing treatments were applied over two five- year terms with a nil-grazing period at the conclusion of each. The latter periods provided a means of measuring the cumulative effects of the grazing treatments. Drought conditions prevailed during the first term so that supplementary feeding was necessary, but the second experienced above average rainfall. Quarterly measurements were made of the pasture dry matter on offer and its botanical and chemical composition. Monthly sheep liveweights, annual wool production and sheep size development in each term were also measured and monetary returns from wool calculated. Rainfall had a major influence on the results recorded and tended to nullify the effects of grazing treatments. Its unpredictability precludes the reliable use of complex techniques in management planning. The overall results suggested that the optimum grazing management of this Mitchell grass rangeland would be continuous grazing at a stocking rate of one sheep to two hectares. Supplementary feeding during drought would be obligatory and should be budgeted for in long-term planning. There was a 50% higher monetary return from this grazing treatment than from the lighter stocking rate and pasture stability (maintenance of Astrebla spp.) was sustained. Pasture stability was adversely affected by the heavier stocking rate. There was no srlstained advantage from rotational grazing compared with continuous grazing.

Sialic acid in colonic mucin: an evaluation of modified PAS reactions in single and combination histochemical procedures

Two new histochemical procedures for detecting sulphated and non-sulphated sialomucin in colonic mucosa were assessed: the saponification-Alcian Blue pH 1-periodic acid-phenylhydrazine-Schiff method (KOH-AB pH 1-PAPS) and the mild periodic acid modification of this (KOH-AB pH 1-mPAS). Using normal colonic mucosa obtained from 11 non-cancer patients, the mPAS and PAPS techniques were tested for specificity and reproducibility for staining sialic acid, either alone or in combination with Alcian Blue. A spectrophotometric method was devised to quantify the uptake of both Schiff and Alcian Blue stain by sections. At low temperature and pH 5.5, the mPAS procedure had improved specificity over the PAPS procedure, and after saponification it could be used to stain O-acetyl-substituted sialic acid. When used in combination with Alcian Blue at pH 1, however, underestimation of the sialic acid content occurred owing to interference between Alcian Blue and Schiff dyes. Interference was even greater with KOH-AB pH 1-PAPS procedure for both sialic acid and sulphate components. We conclude that caution must be exercised in interpretation of the staining results obtained with these new combination methods and that more accurate information on the sialic acid and sulphate content of colonic mucin is obtained by staining serial sections with the mPAS technique and Alcian Blue pH 1 alone.

Nonspecific airway hyperreactivity in nonsmoking bituminous coal miners demonstrated by quantitative methacholine inhalation challenge

Because nonsmoking underground bituminous coal miners often have symptoms of chronic bronchitis and because a high proportion of patients with chronic bronchitis have nonspecific airway hyperreactivity, we hypothesized that coal miners would have a higher prevalence of nonspecific airway hyperreactivity than nonminer nonsmoking control subjects. By use of a quantitative methacholine provocative inhalation challenge test, we evaluated 22 underground bituminous coal miners and 41 nonminer age- and sex-matched control subjects from the same community. We found that a significantly higher proportion of miners had reactivity to inhalation of 100 mg/ml or less of methacholine, X2 = 6.19, p less than 0.02. The slope of phase III of the single-breath nitrogen washout test was higher in the reactive miners than in the nonreactive miners and reactive control subjects, even though the reactive miners had only been working underground 8 +/- 3 (SEM) years. Within the reactive miner subgroup, the higher the reactivity to methacholine, the more abnormal the slope of phase III of the single-breath nitrogen test, r = 0.79. Miners had more symptoms than controls; the presence of methacholine reactivity was not associated with increased symptoms. We conclude that the bituminous coal miners in our study had an increased prevalence of nonspecific airway hyperreactivity and that within the reactive miner subgroup there was evidence of early airways disease. We speculate that the nonspecific airway hyperreactivity may be related to, and also be an indicator of, lung injury in coal miners.

Proliferative instability and experimental carcinogenesis at colonic anastomoses

The possibility that proliferative instability around a healing anastomosis promotes carcinogenesis was tested in 234 male Sprague-Dawley rats. Animals received the first of five weekly injections of azoxymethane (total dose 50 mg/kg) either immediately after transection of the descending colon or at 2, 4, 8, and 12 weeks later; controls received handling of the bowel alone. Crypt cell proliferation was assessed by autoradiography following 3HTdR injection. An overall increase in tumour yields in all transection groups was due solely to the frequent presence of anastomotic tumours. Changes in crypt morphometry and labelling index were most marked in crypt positions 1-10 away from the anastomosis. Crypts at this site increased in height at 2, 4, and 8 weeks (p less than 0.001) but returned to normal values by 12 weeks. Likewise, labelling index was increased at 2, 4, and 8 weeks (p less than 0.001) and remained higher at 12 weeks (p less than 0.05). Increased crypt cell proliferation in the immediate vicinity of an apparently 'healed' colonic anastomosis may explain its persisting susceptibility to carcinogenesis.

Kinetics of divalent monoclonal antibody binding to tumour cell surface antigens using flow cytometry: standardization and mathematical analysis

Flow cytofluorimetric methods have been used to quantitate the interaction between a divalent monoclonal antibody and a tumour cell surface antigen. After standardization using fluorescein and 125I-labelled antibodies, kinetics of association and dissociation were measured, and antibody bound at equilibrium quantitated. A mathematical model was developed in conjunction with these experimental results which allowed the calculation of rates for monovalent association and monovalent and divalent dissociation, and a description of the contribution of each to the level of bound antibody at different antibody concns.

Relationship of serum naproxen concentration to efficacy in rheumatoid arthritis

Twenty-four patients with rheumatoid arthritis were tested in a randomized, double-blind. Latin-square comparison of 250, 750 and 1500 mg of naproxen daily. Each received each dose for 2 wk and baseline disease activity was established during withdrawal of medication before and after the study. Nine standard measures of efficacy were tested at each evaluation. No order effect or change in baseline was found. Total and unbound naproxen concentrations were measured by high-pressure liquid chromatography and equilibrium dialysis, respectively. A linear dose-response relationship (P less than 0.05) was demonstrated between naproxen and joint count, patient's pain assessment, activities of daily living index, physician's global assessment, and grip strength. The relationship to patients' global assessment was of uncertain significance (P less than 0.07). A positive dose to serum level correlation (1, 2, and 12 hr after dose) was apparent (r greater than 0.78). When patients were defined as responders or nonresponders by a summed efficacy score, there was a serum concentration-response relationship; the percentage of responding patients increased with each serum level quartile: 25%, 31%, 59%, and 75%. Patients with a trough total serum naproxen concentration under 18 micrograms/ml did not respond, while 76% of patients with trough total serum concentrations above 50 micrograms/ml responded. No serum naproxen toxicity level relationship was established.

Humoral immune responses in murine pregnancy. II. Kinetics and nature of the response in females preimmunized against paternal alloantigens

The kinetics of anti-paternal alloantibody production in syngeneically and allogeneically mated mice previously immunized with allogenic spleen cells has been investigated. In allogeneically mated females, total and cytotoxic alloantibody levels increased during the final 3 days of pregnancy to reach maximal levels around 1 week after parturition. The properties of this alloantibody were indistinguishable from those of alloantibody induced by conventional immunization procedures. In syngeneically mated females no increase was observed. Total hysterectomy demonstrated that the immunogenicity of the conceptus required to produce a secondary humoral immune response was initiated in the majority of females between days 9 and 10 of pregnancy, and that the antigenic exposure by day 10 was sufficient to induce a maximal secondary response. These observations were consistent with the time of appearance of serologically demonstrable H-2 antigens on embryonic cells during pregnancy. These phenomena occurred in 'responder' and 'non-responder' female strains (referring to the ability of allogeneically mated females to produce anti-paternal alloantibody during normal pregnancy) demonstrating that they do not differ in their ability to produce a secondary immune response to alloantigens presented via the intrauterine route. The findings are discussed in relation to the nature of the immunogenic stimulus from the concepts in this system and during pregnancy.

A small arterial substitute: expanded microporous polytetrafluoroethylene: patency versus porosity

Eighty-nine grafts of expanded microporous polytetrafluoroethylene (PTFE) with a diameter of 4 mm, were placed in the carotid and femoral arteries of dogs. The animals were sacrificed at varying intervals beginning three days after operation. Four animals remain alive with patent grafts 10 months post-operatively. Twenty-four of 89 grafts were occluded, an overall patency of 73%. Fibril length (pore size) of the graft material was varied from 4 to 110 microns. Average pore size ranged from 9 to 65 microns. Wall thickness varied from 0.3 to 0.75 mm. Density ranged from 0.24 to 0.35 g/ml. Tissue ingrowth, neointimization and patency rate as compared to pore size, wall-thickness and density of expanded PTFE were observed. Pore size is the primary determinant of tissue ingrowth, neointimization and patency. Of 51 grafts with an average pore size of 22 microns or less, there were 6 occlusions, an 88% patency rate. There were 38 grafts with an average pore size of 34 microns or greater. In these 38 grafts, 18 occlusions were observed, a 53% patency rate. Patent grafts demonstrated tissue ingrowth, capillary formation an a thin neointima. Using small pore grafts, patency rates of 90% can be anticipated in the dog. Expanded microporous PTFE with its ease of handling, strength and pliability may be the vascular prosthesis of choice in man.

Grazing management of native pastures in the New England region of New South Wales. II. The effect of size of flock on pasture and sheep production with special reference to internal parasites and grazing behaviour

The effect of flock size on pasture and animal productivity, on parasitic infection, and on grazing behaviour was investigated in a grazing experiment over a period of 3 years. Merino sheep, undrenched, and stocked at the rate of one sheep per acre on native pasture dominated by Bothriochloa ambigua S.T. Blake, were used in five flock sizes, vie. 2, 4, 8, 16, and 30 animals. Flock size did not significantly affect the forage available or the botanical composition of the pastures, but liveweight gains and wool production were significantly lower in the flock of two sheep than in the other flocks. Observations indicated that the reduced productivity of the smallest flock was associated with reduced grazing time consequent on changes in grazing behaviour. No consistent significant differences in worm egg counts were observed in faecal samples from the different flocks. The results indicate that although under fairly extensive grazing conditions a unit of two sheep may be unsatisfactory in some respects, flocks of four sheep could give information on pasture or animal production or on parasitism comparable with that from larger flocks of up to 30 animals.

Grazing management of native pastures in the New England region of New South Wales. I. Pasture and sheep production with special reference to systems of grazing and internal parasites

In a 4-year grazing experiment with Merino sheep, on a native pasture dominated by Bothriochloa ambigua S.T. Blake, three rates of stocking and continuous v. rotational grazing were compared. The effects of these treatments on the forage available and the botanical composition of the pasture and on sheep liveweights, size of sheep, wool production, wool fibre diameter, and parasitic infestation, both with and without drenching with phenothiazine, mere studied. The effects of seasonal conditions on the above and on the chemical composition of the pasture were also recorded. No consistently significant differences between grazing treatments in their effects on the pasture or on sheep liveweights or parasitic infestation were recorded, although during the final 3 years the total forage available was less under heavy stocking. Seasonal variations in total forage mere not marked, but, production of green forage increased greatly in the spring and declined to a very low level during winter. Similarly, sheep liveweights increased during spring and summer and declined in the winter. These liveweight changes were significantly correlated with the amount of green forage available. Wool fibre diameter showed similar seasonal fluctuations but the maximum diameter was attained earlier than maximum liveweight. Coincident with a spring rise in the amount of green forage there was also an increase in the percentages of crude protein and phosphorus in the green components of the pasture. Liveweight gains of the drenched sheep were significantly greater from the beginning of each experimental year in the late spring (November) to late winter (August) in all stocking treatments. In the spring, when the quality of the pasture improved and worm egg counts were low, drenching had no effect on liveweight gains in three out of four years. Drenching also significantly improved wool production and resulted in an increase in skeletal size of sheep in three out of four years. Drenching reduced egg counts of the parasites Oesophagostomum spp. and Haemonchus contortus (Rudolphi) Cobb but was less effective against Trichostrongylus-Ostertagia spp. For all grazing treatments there was no significant difference in the amount of wool produced per head, but over the 4-year period 56 per cent. more wool per acre was produced from the heavy than from the light rate of stocking.