Transcript of a homolog of aflR, a regulatory gene for aflatoxin synthesis in Aspergillus parasiticus, was not detected in Aspergillus oryzae strains

Some strains of Aspergillus oryzae were shown to have homologs of aflR, a regulatory gene for aflatoxin synthesis in Aspergillus parasiticus. Transcription of an aflR homolog was examined in six strains of A. oryzae having the homologs, using polymerase chain reaction (PCR) coupled with reverse transcription. No PCR product was obtained when the RNA prepared from the A. oryzae strains cultivated under aflatoxin-producing condition was used as template for amplification of the aflR cDNA. By contrast, a PCR product of the expected size was obtained with RNA from A. parasiticus NIAH-26 processed by the same procedure. From genomic DNA of these strains, PCR products of the same size as above were obtained. Possible degradation of the aflR mRNA in the RNA preparation of the A. oryzae strains was negligible, because the calmodulin transcript was detected by PCR from the same RNA samples. Thus, the aflR homologs in the non-aflatoxigenic A. oryzae strains examined are not expressed even under aflatoxin-producing condition.

Thieno[2,3-d]pyrimidine-3-acetic acids. A new class of nonpeptide endothelin receptor antagonists

On the basis of structural information for the cyclic hexapeptide endothelin (ET) receptor antagonist, TAK-044, a series of thieno[2,3-d]pyrimidine-2,4-dione derivatives bearing a carboxyl group and aromatic rings that were important for receptor binding were designed, synthesized, and evaluated for ET receptor binding affinities and inhibitory activities against ET-induced vasoconstriction. Optimization of each substituent in the thieno[2,3-d]pyrimidine ring led to the discovery of a novel and potent nonpeptide ET receptor antagonist, 6-(4-methoxymethoxyphenyl)-5-methylsulfonylaminomethyl-1-(2- methylthiobenzyl)-2,4-dioxo-1,2,3,4-tetrahydrothieno[2,3-d]p yrimidine-3- acetic acid (32 g), which binded to human ETA and ETB receptor subtypes with affinities (IC50) of 7.6 and 100 nM, respectively. Compound 32 g effectively antagonized ET-induced vasoconstriction and the inhibitory effect mediated by the ETB receptor was more potent than that of bosentan, while the inhibitory effect mediated by the ETA receptor was slightly less potent than that of bosentan.

The blood flow patterns of microsurgical procedures in rats with topical and systemic vasodilators

The change in blood flow after anastomosis and the effects on the anastomosed artery of different classes of vasodilators such as lidocaine and chlorpromazine given topically (n = 10 in each group), and prostaglandin E1 (PGE1)(n = 12) and diltiazem hydrochloride (n = 10) given systemically, were investigated in the femoral arteries of rats. The blood flow after anastomosis decreased by 45%-60% compared with that before the anastomosis. Lidocaine showed almost the same pattern of blood flow as chlorpromazine. The former dilated the diameter of the vessel less than the latter, and the depression of the heart rate was less with lidocaine than in chlorpromazine. PGE1 had a longer and stronger vasodilatative action than diltiazem, and resulted in a remarkable increase in blood flow. Clinically, the topical application of chlorpromazine or lidocaine is recommended during an operation, and PGE1 should be given systemically after an operation to obtain adequate blood flow.

Neutrophils responded to immobilized lipopolysaccharide in the absence of lipopolysaccharide-binding protein

Lipopolysaccharide (LPS) in solution primes neutrophils for enhanced release of superoxide in response to N-formyl-methionyl-leucyl-phenylalanine. We show that LPS immobilized on polystyrene or polypropylene acted on neutrophils by a mechanism different from that of LPS in solution. Coating the surface with 1% plasma, either before coating with LPS (plasma/LPS) or after coating with LPS (LPS/plasma), was essential to induce the LPS response in neutrophils. However, plasma could be replaced by fibrinogen, type I collagen or type IV collagen, or, to a lesser extent, by fibronectin or vitronectin, which was not true for LPS in solution. About 20% of the LPS added was immobilized on the plastic surfaces, based on its ability to adsorb anti-LPS antibody after extensive washing. The amount of soluble LPS that might have been released from surfaces during the incubation with neutrophils was too low to account for the priming by immobilized LPS. About 13-20 min was needed for neutrophils to become primed after incubation with immobilized LPS. Immobilized LPS induced up-regulation of CD11b/CD18 and latent alkaline phosphatase and also enhanced the adhesive response of neutrophils. Priming by immobilized LPS was inhibited by anti-CD14 antibody or by treatment of neutrophils with the LPS antagonist LA-14-PP. When immobilized LPS was treated with anti-LPS-binding protein (LBP) antibody, the response of neutrophils to LPS/plasma was inhibited but the response to plasma/LPS or fibrinogen/LPS was not. Thus, the LPS in plasma/LPS or fibrinogen/LPS acted on neutrophils in an LBP-independent manner. We conclude that the CD14-dependent LPS receptor system of neutrophils was capable of working in the absence of LBP, but only when LPS was immobilized on a surface coated with protein.

Prefabricated muscle flap including bone induced by recombinant human bone morphogenetic protein-2: an experimental study of ectopic osteoinduction in a rat latissimus dorsi muscle flap

For skeletal reconstruction, a vascularised bone graft is both reliable and useful, but some sacrifice usually occurs at the skeletal donor site. In the search for our alternative, we investigated ectopic osteoinduction by bone morphogenetic protein in a rat muscle flap, to prefabricate a muscle flap that included bone. Right latissimus dorsi muscle flaps were prepared in 16 rats. Recombinant human bone morphogenetic protein-2 (rhBMP-2; 2, 10 and 50 micrograms) mixed with atelopeptide type I collagen (3 mg) as the carrier was wrapped with the tip of the latissimus dorsi muscle flap. Three weeks later, ectopic osteoinduction in the latissimus dorsi muscle flap was investigated radiologically, histologically and biochemically. A radiological oval shadow was observed in each animal in each rhBMP-2-implanted group. The volume of the oval shadow area in the muscle flap was dependent upon the dosage of rhBMP-2. It indicated that on ectopic osteoinduction by rhBMP-2 in the muscle flap, induced trabeculae were circularly constructed at the margins of the lump. The radio-opacity of the oval shadows was almost equal in all rhBMP-2-implanted groups, and the shadow areas depended on the dosage of rhBMP-2. The biochemical indices of osteogenesis, ALP activity and Ca content in the lump were dependent upon the dosage of rhBMP-2. This study showed that ectopic osteoinduction occurred in the rat latissimus dorsi muscle flap and depended upon the dose of rhBMP-2. Wrapping rhBMP-2 mixed with atelopeptide type I collagen with the tip of a latissimus dorsi muscle flap could create a prefabricated muscle flap that included bone.

Osteoinduction capability of recombinant human bone morphogenetic protein-2 in intramuscular and subcutaneous sites: an experimental study

The osteoinduction capability of recombinant human bone morphogenetic protein-2 (rhBMP-2) in the muscle and in the subcutaneous tissue in Wistar rats (n = 20) was evaluated, using atelopeptide type-I collagen as a carrier. The alkaline phosphatase (ALP) activity and calcium (Ca) content were quantitatively analyzed 1, 3, 7 and 21 days after the implantation of 5 micrograms of rhBMP-2. At 3 days, the ALP activity began to increase gradually. The Ca content showed a slow increase until 7 days and was markedly elevated at 21 days. There was no significant difference observed between the intramuscular and subcutaneous sites until 3 days. However, at 7 days, both the ALP activity and Ca content were significantly higher intramuscularly than subcutaneously. Also, at 21 days they were higher in the muscle than in the subcutaneous tissue. These results suggest that the difference in osteoinduction could be related to the partial pressure of oxygen or the blood supply in the intramuscular and subcutaneous sites, and that immature mesenchymal cells in the muscle could more easily differentiate into osteoblasts, leading to osteoinduction. This study clearly demonstrated that even a small amount (5 micrograms) or rhBMP-2 induces new bone in the subcutaneous tissue, which has a lesser blood flow than the muscle.

[Mycobacterial lung infection in 8 patients with AIDS: clinical and radiological features]

The prevalence of mycobacterial infection in AIDS patients has increased in Japan. This report describes details of the clinical and radiological features of eight AIDS patients with mycobacterial disease (6 with M. tuberculosis infection and 2 with M. kansasii infection) in our hospital during the period from October 1995 through February 1997. Six of the 8 were men, and two were women. The mean age was 36.5 years. Six were Japanese, one was from Myanmar, and one was Malaysian. The median CD4 positive T lymphocyte counts (CD4 count) at the time of diagnosis of the M. tuberculosis was 75.5 (range 14-569/microliter, and the M. kansasii was 21.5 (range 19-24)/microliter. Clinical findings and symptoms of all patients were non-specific, but almost all patients had a cough and fever. In the radiographic findings, the patients of the M. tuberculosis group presented multiple hilar and mediastinal lymphadenopathy, miliary shadow, and obstructive pneumonia. Both M. kansasii patients showed a multiple infiltration shadow. There were no drug resistant strains in M. tuberculosis except on isolate with moderate resistant. to Streptomycin. These observations suggest that AIDS-associated mycobacterial disease shows atypical clinical and radiological features in some cases, especially in advanced stages of AIDS. Therefore, we need to recognize the characteristics of the clinical and radiological features of the patients with mycobacterial diseases and AIDS.

Intramuscular osteoinduction and bone marrow formation by the implantation of rhBMP-2 with atelopeptide type I collagen

The study examines the osteoinductive potential of recombinant human morphogenetic protein 2 (rhBMP-2) radiologically and histologically in rat calf muscle. Ten male Wistar rats were used. rhBMP-2 50 microg was implanted with atelopeptide type I collagen as carrier in a pouch in rat calf muscle (n = 5), and atelopeptide type I collagen alone was implanted in a further five as control. Induction of osteogenesis at 4 weeks was investigated. In all rats in which rhBMP-2 had been implanted there was a radio-opaque shadow in the muscle in the soft tissue radiograph. No such shadows were noted in the control group. Histological examination showed bony trabeculum, osteoblasts, and vigorous bone marrow including fatty marrow and angioid tissue both at the margins and in the center of the excised lumps in the rhBMP-2 group. There were no such signs in the control group. rhBMP-2 may be capable not only of inducing the formation of bone, but also of inducing a 'self-supporting bone organ' in the muscle.

Comparison of ectopic osteoinduction in vivo by recombinant human BMP-2 and recombinant Xenopus BMP-4/7 heterodimer

Two micrograms recombinant human bone morphogenetic protein-2 (rhBMP-2) and 2 microg recombinant Xenopus bone morphogenetic protein-4/7 heterodimer (rxBMP-4/7ht) were implanted into a calf muscle pouch in rats using atelopeptide type I collagen (CL) solution as the carrier. Three weeks later induced bone in the rhBMP-2 + CL group (group A; n=5) and the rxBMP-4/7ht + CL group (group B; n=5) was investigated radiologically and histologically. Bone trabeculum and marrow were induced in all cases of both groups. In group A the area of radioopaque oval shadows was 5.78 mm2, wider than 4.64 mm2 in group B. The radoopacity in group A was 74.6, higher than 57.6 in group B. Histometry of the microscopic views showed that the trabecular area was 0.92 mm2 in group A and 0.22 mm2 in group B, while the trabecular percentage occupied in the overall lump area was 18.07% in group A and 5.51% in group B. The trabecular form in group A was more massively coral than in group B. This study indicated that rhBMP-2 has a higher ectopic osteoinduction ability in vivo than rxBMP-4/7ht.

Electrolyzed-reduced water scavenges active oxygen species and protects DNA from oxidative damage

Active oxygen species or free radicals are considered to cause extensive oxidative damage to biological macromolecules, which brings about a variety of diseases as well as aging. The ideal scavenger for active oxygen should be 'active hydrogen'. 'Active hydrogen' can be produced in reduced water near the cathode during electrolysis of water. Reduced water exhibits high pH, low dissolved oxygen (DO), extremely high dissolved molecular hydrogen (DH), and extremely negative redox potential (RP) values. Strongly electrolyzed-reduced water, as well as ascorbic acid, (+)-catechin and tannic acid, completely scavenged O.-2 produced by the hypoxanthine-xanthine oxidase (HX-XOD) system in sodium phosphate buffer (pH 7.0). The superoxide dismutase (SOD)-like activity of reduced water is stable at 4 degrees C for over a month and was not lost even after neutralization, repeated freezing and melting, deflation with sonication, vigorous mixing, boiling, repeated filtration, or closed autoclaving, but was lost by opened autoclaving or by closed autoclaving in the presence of tungsten trioxide which efficiently adsorbs active atomic hydrogen. Water bubbled with hydrogen gas exhibited low DO, extremely high DH and extremely low RP values, as does reduced water, but it has no SOD-like activity. These results suggest that the SOD-like activity of reduced water is not due to the dissolved molecular hydrogen but due to the dissolved atomic hydrogen (active hydrogen). Although SOD accumulated H2O2 when added to the HX-XOD system, reduced water decreased the amount of H2O2 produced by XOD. Reduced water, as well as catalase and ascorbic acid, could directly scavenge H2O2. Reduce water suppresses single-strand breakage of DNA b active oxygen species produced by the Cu(II)-catalyzed oxidation of ascorbic acid in a dose-dependent manner, suggesting that reduced water can scavenge not only O2.- and H2O2, but also 1O2 and .OH.

Self-regenerating bone implant: ectopic osteoinduction following intramuscular implantation of a combination of rhBMP-2, atelopeptide type I collagen and porous hydroxyapatite

A combination of recombinant human bone morphogenetic protein-2 (rhBMP-2), atelopeptide Type I collagen (CL) as a carrier and porous hydroxyapatite (pHAP) was implanted in a calf muscle pouch of the rat. Three rhBMP-2-implanted groups (2, 10 and 50 micrograms; each n = 5) and the control group (n = 5), in which only CL and pHAP were implanted, were established. Three weeks later, the implants were examined.

Study of the changes of serum hyaluronic acid during porcine liver transplantation: influence of warm ischemia

Twelve porcine liver transplantations were performed to investigate whether serum hyaluronic acid (HA) serves as a marker of warm ischemic injury. Group 1 was a control without warm ischemia (n = 7), and pigs in Group 2 were sacrificed by intracardiac KCl injection 60 min before harvesting (n = 5). All pigs survived more than 4 days in Group 1. In Group 2, all died within 2 days due to graft failure. Arterial and hepatic venous glutamic-oxaloacetic transaminase (GOT) in Group 2 were higher after revascularization. However, there were no differences between the 2 groups in arterial and hepatic venous HA levels. HA clearance by the graft also showed no differences between the groups. Although GOT reflected the degree of warm ischemia, HA and its hepatic clearance were not influenced by warm ischemic damage. In conclusion, HA was not thought to serve as a marker of liver injury when the graft suffered from warm ischemia.

Purification and characterization of the esterases involved in aflatoxin biosynthesis in Aspergillus parasiticus

The esterases from the cell-free extracts (CFEs) of Aspergillus parasiticus ATCC15517, an aflatoxin-producing strain, catalyzing the hydrolytic conversion of versiconal hemiacetal acetate (VHA) to versiconal was biochemically studied. The specific activity of the enzymes increased 2.5-fold during incubation of mycelia through 40-55 h. No metal ions were required for enzyme stability, but EDTA at 1 mM and dithiothreitol at 0.5-5 mM increased its stability. Three peaks of VHA esterase activity were resolved when the proteins in the CFEs prepared from the mycelia of different ages were separated by anion-exchange column chromatography, suggesting that at least three VHA esterases were present in the eluate of this purification step. One of these esterases extracted from the mycelia of a 55-h culture was partially purified in five steps by means of preparative chromatography and fast protein liquid chromatography. The partially purified enzyme when reacted with [14C]diisopropylfluorophosphate followed by sodium dodecyl sulfate - polyacrylamide gel electrophoresis gave a single radiolabelled band, which corresponded to a protein of 32 kDa. The molecular mass of the partially purified VHA esterase determined with gel filtration was around 60 kDa. The results suggested that the enzyme consists of two isomeric subunits.

[A case of right postpneumonectomy empyema treated by open window thoracostomy, thoracoplasty, pedicled omental flap and musculocutaneous flaps]

A case of right postpneumonectomy empyema treated by open window thoracostomy, thoracoplasty, pedicled omental flap and musculocutaneous flaps is reported. After open window thoracostomy, pedicled omental flap and musculocutaneous flaps transplantation utilizing techniques used in plastic surgery were performed, and right postneumonctomy empyema was successfully treated. In this study, open window thoracostomy was effective against depuration of the empyema cavity and omental and musculocutaneous flaps against the infection control and plombage of the cavity. Furthermore, to maximize the effect of musculocutaneous flaps and to use them effectively, it is thought that techniques utilized in plastic surgery are effective and necessary.

Pharmacological characterization of cardiovascular responses induced by endothelin-1 in the perfused rat heart

The effects of the endothelin receptor antagonist TAK-044 (cyclo[D-alpha-aspartyl-3-[(4-phenylpiperazin-1-yl)carbonyl]-L-ala nyl-L-alpha-aspartyl-D-2-(2-thienyl)glycyl-L-leucyl-D-tryptophyl]+ ++disodiu m salt) and BQ-123 (cyclo[D-Asp-Pro-D-Val-Leu-D-Trp]) were studied in the rat heart to characterize the receptor subtypes responsible for the cardiovascular actions of endothelin-1. Endothelin-1 induced a transient decrease and subsequent increase in perfusion pressure in perfused rat hearts, and increased left ventricular developed pressure. TAK-044 diminished these endothelin-1-induced responses (100 pmol/heart) with IC50 values of 140, 57 and 1.3 nM, respectively. BQ-123 (1-30 mu M) partially inhibited the endothelin-1-induced hypertension (30-40%) in the rat heart, and failed to inhibit the hypotension. The positive inotropic effect of endothelin-1 was abolished by BQ-123. Neither indomethacin (10 mu M) nor Nomega-nitro-L-arginine methyl ester (100 mu M) attenuated the endothelin-1-induced hypotension. TAK-044 and BQ-123 attenuated the positive inotropic effect of endothelin-1 in rat papillary muscles. In rat cardiac membrane fractions, TAK-044 and BQ-123 inhibited [125I]endothelin-1 binding to endothelin ET(A) receptors with IC50 values of 0.39 +/- 0.6 and 36 +/- 9 nM, respectively, whereas only TAK-044 potently blocked the endothelin ET(B) receptor subtype (IC50 value: 370 +/- 180 nM). These results suggest that endothelin-1 modulates cardiovascular functions in the rat heart by activating both endothelin ET(A) and endothelin ET(B) receptors, all of which are sensitive to TAK-044.

An analogue of lipid A and LPS from Rhodobacter sphaeroides inhibits neutrophil responses to LPS by blocking receptor recognition of LPS and by depleting LPS-binding protein in plasma

When incubated with lipopolysaccharide (LPS) in the presence of plasma, neutrophils become primed for enhanced release of superoxide in response to triggering by formyl-Met-Leu-Phe (fMLP). The effect of LPS on phagocytes is inhibited by a synthetic lipid A precursor, LA-14-PP (lipid IVa) or by LPS from Rhodobacter sphaeroides (Rs). We studied the mechanisms by which LA-14-PP or Rs-LPS inhibited LPS-induced responses. When neutrophils were exposed to LA-14-PP or Rs-LPS for 3 min and then to Escherichia coli-LPS, the antagonists inhibited priming for superoxide release, and also blocked up-regulation of CD11b and adherence. This inhibition was dependent on plasma, was not overcome by higher amounts of E. coli-LPS or plasma, and was not observed at 0 degrees C, suggesting that E. coli-LPS was not able to interact with its receptor or other cellular recognition molecule in neutrophils that had been exposed to the antagonists. The alternative possibility that LA-14-PP or Rs-LPS depleted a plasma cofactor, resulting in inhibition of priming, was investigated by using LPS from Porphyromonas gingivalis (Pg) and Bordetella pertussis (Bp). These LPS primed neutrophils in a plasma-dependent and CD14-dependent manner, but were not blocked by LA-14-PP or Rs-LPS. When sub-optimal concentrations of plasma were exposed to LA-14-PP or Rs-LPS, and then mixed with Pg-LPS or Bp-LPS, followed by incubation with neutrophils, priming and up-regulation of CD11b were inhibited, and this inhibition was overcome by increasing the concentration of plasma. Binding of LPS-binding protein (LBP) in plasma to immobilized E. coli-LPS was inhibited by pre-incubation of plasma with LA-14-PP or Rs-LPS. Together with the result that treatment of plasma with anti-LBP antibody abolished the cofactor activity of plasma, these results indicated that LA-14-PP and Rs-LPS depleted LBP from plasma, resulting in inability of LPS to act on neutrophils. Thus LA-14-PP and Rs-LPS inhibited the action of LPS on neutrophils by at least two mechanisms, blocking of LPS receptor recognition and depletion of the cofactor LBP.

Comparative study of bone marrow induced by purified BMP and recombinant human BMP-2

Into a calf muscle pouch in Wistar rats, 50 micrograms purified bone morphogenetic protein (pBMP) or 50 micrograms recombinant human bone morphogenetic protein-2 (rhBMP-2) was implanted using atelopeptide type I collagen solution (CL) as a carrier. Three weeks later bone and bone marrow were induced in both groups. These induced bone and bone marrow were studied histologically. In the pBMP+CL group (n = 5), rich bone matrix and little bone marrow were observed. There was no fatty marrow or angioid tissue observed. In the rhBMP-2+CL group (n = 5), bone matrix and rich marrow including fatty marrow and angioid tissue were observed around and among the bony trabeculae. It was suggested that a "self-supporting bone organ" was induced.

Increase in length of experimental skin flaps that survive with dibutyryl cyclic AMP

One of the most important research topics in plastic surgery is the extension of the length of skin flaps that survive. We have investigated the increase in the length of skin flaps that can be achieved by giving dibutyryl cyclic AMP (DB-cAMP) to rabbits with experimental skin flaps and compared the results with those in animals not given DB-cAMP. Three variables, the arrival of DB-cAMP in the critical area of circulation of the flap (n = 6), changes in the blood flow in the flap (n = 10), and increase in the length of skin flap that survived (n = 30) were investigated by high performance liquid chromatography and laser Doppler flowmetry. DB-cAMP reached the critical area of circulation in the skin flap (dye distance), increased the blood flow within this area (mean (SEM) peak value 30 minutes after operation 1.24 (0.06) ml/min/kg compared with 1.06 (0.02) in control flaps), and extended the length of the flap that survived (mean (SEM) length seven days after operation 66.1 (3.0) mm compared with 60.8 (1.8) mm in the control group). We conclude that DB-cAMP improved the blood flow in skin flaps in rabbits with a consequent increase in the length of skin flap that survived.

[A case of ANCA negative Wegener's granulomatosis with pulmonary giant bulla showing high level of soluble ICAM-1]

This paper reports a rare case of the limited form of Wegener's granulomatosis (WG) with pulmonary giant bulla, which was pathologically identified only in the lung and showed a high level of soluble intercellular adhesion molecule-1 (ICAM-1) but not anti-neutrophil cytoplasmic antibody (ANCA). A 46 year-old male was admitted for the further examination of right anterior chest pain and dyspnea. Chest X-ray and CT examination showed giant bulla accompanied with the invasive lesions in upper lobe of right lung. Partial lobectomy was done. Granulomatous and necrotizing vasculitis characteristics of WG were confirmed by the histopathology of resected tissues. Immunological analysis on admission showed a high level of soluble ICAM-1 and ANCA negative, but that of soluble ICAM-1 was reduced after surgical operation and remained within normal range during an administration of prednisolone and cyclophosphamide. These results suggest that soluble ICAM-1 may be one of the useful parameters for a diagnosis of WG and for an estimation of its treatments, especially in the cases of ANCA negative WG.

Eradication of poliomyelitis: progress in the People's Republic of China

China and the other countries of the Western Pacific Region have a goal of eradication of wild poliovirus by the end of 1995. In this report we examine the progress made toward eradication through the end of 1993. We examined the information about poliomyelitis and wild poliovirus based on the acute flaccid paralysis surveillance system. The number of reported poliomyelitis cases decreased from 4623 cases in 1989 and 5065 cases in 1990, which occurred during a large nationwide poliomyelitis epidemic, to 538 cases in 1993. Mass supplemental immunization sessions were conducted during the 1991 to 1992 and 1992 to 1993 winters. After the two rounds of supplemental immunizations in the 1992 to 1993 winter, wild poliovirus was not detected for the subsequent 21 months in 22 contiguous provinces in central and northern China, in which 980 million persons reside. In 1993 wild poliovirus was detected in only 5 provinces in southern China and in 2 provinces in the remote Western region; these provinces have only 14% of the total population in China. China is close to achieving its 1995 poliomyelitis elimination goal. Mass supplemental immunizations in children 0 to 3 years old can rapidly eliminate wild poliovirus from large, very densely populated areas, low income rural areas and remote mountainous areas. There appears to be no technical obstacle, even in the most difficult areas, to achieving global eradication of wild poliovirus by the year 2000.