A second form of phenylalanine ammonia-lyase from leaf mustard

Phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) catalyzes the elimination of ammonium ion from L-phenylalanine in a variety of plants and fungal species. PAL was previously purified and characterized from leaf mustard in our laboratory. In the present study, we purified a second phenylalanine ammonia-lyase (PAL II) from leaf mustard by a combination of ion exchange chromatography and gel filtration. PAL I and PAL II migrate at a different rate on native polyacrylamide gel electrophoresis. It consists of four subunits, each having the molecular mass of about 37,000 Da. Its isoelectric point and Km value for L-phenylalanine were found to be 5.4 and 3.8 x 10(-5)M, respectively. The purified enzyme has an optimum pH and temperature of 8 and 45 degree C, respectively. It is activated about 2-fold by caffeic acid (1 mM), whereas it is inhibited to 15% by Zn2+ (1 mM). However, the physiological role of PAL II remains unknown.

Gene frequencies of eight human platelet-specific antigens in Koreans

Human platelet-specific antigens (HPAs) are found on platelet membrane glycoproteins and are the target of platelet alloantibodies that mediate platelet destruction in neonatal alloimmune thrombocytopenia (NAIT), post-transfusion purpura (PTP) and refractoriness to platelet transfusion therapy. The biallelic polymorphism of all HPA systems is known to be due to a substitution of a single base pair. This study was performed to investigate the frequency of the HPA genes in Koreans, based on these substitutions. The genotypes of eight HPA systems were determined by polymerase chain reaction using sequence-specific primers (PCR-SSP) for HPA-1, -2, -4, -5, and -8 and restriction fragment length polymorphism (RFLP) for HPA-3, -6, and -7. The gene frequencies obtained from 200 unrelated Koreans were 0.99 and 0.01 for HPA-1a and -1b, 0.92 and 0.08 for HPA-2a and -2b, 0.55 and 0.45 for HPA-3a and -3b, 0.99 and 0.01 for HPA-4a and -4b, 0.98 and 0.02 for HPA-5a and -5b, and 0.98 and 0.02 for HPA-6a and -6b. All the individuals tested were homozygotes for HPA-7a and HPA-8a. It has been reported that the HPA-1b antigen is extremely rare (less than 0.3%) in Oriental populations, but this study suggests that the frequency of this antigen in Koreans (2.0%) is higher than in Japanese and Chinese populations.

Autogenous tissue-engineered cartilage: evaluation as an implant material

OBJECTIVES

To determine whether autogenous tissue-engineered cartilage grafts can be synthesized in predetermined shapes, to compare tissue-engineered cartilage with native cartilage with respect to histological characteristics and biomechanical properties, and to demonstrate how multiple transplantations affect tissue-engineered cartilage.

DESIGN

Controlled, prospective animal study.

SUBJECTS

Twenty New Zealand white rabbits, 3 weeks old.

INTERVENTIONS

Autogenous chondrocytes were seeded onto biodegradable polyglycolic acid-poly-L-lactic acid copolymer templates in 1 of 3 shapes (cross, nasal tip graft, or auricle). Grafts and controls of sculpted cartilage were divided among 3 groups: short-term implantation (4 or 8 weeks), long-term implantation (6 or 12 months), and a reimplantation group. The gross morphological features, histological findings, and tensile strength of grafts were assessed.

RESULTS

Production of tissue-engineered cartilage was confirmed in 30 of 31 implants. Histological evaluation demonstrated characteristic cartilaginous matrix, but with prominent vascular and fibrous tissue ingrowth. In long-term implantation grafts (n=4), foci of osteoid were evident by 6 months. In the subset of transplanted grafts (n=7), 5 of 7 demonstrated significant loss of cartilage viability. Tensile strength measurements demonstrated values 24% and 41% of those of controls at 4 and 8 weeks, respectively.

CONCLUSIONS

Tissue-engineered autogenous cartilage can be reliably produced, and predetermination of graft shape is possible. Histologically, grafts represent composites of mature cartilage infiltrated by vasculature and fibrous tissue, with delayed osteoid formation. Graft viability is compromised by early transplantation, and tensile strength is less than that of native cartilage. These results demonstrate the feasibility of tissue-engineered cartilage as a future graft material.

Immunohistochemical localization of ganciclovir in the human retina

PURPOSE

To localize ganciclovir in the retina of human eyes treated with intravenous or intravitreal ganciclovir for cytomegalovirus (CMV) retinitis.

METHODS

Paraffin-embedded five-micron sections of autopsy eyes were obtained from seven patients as follows: two patients with CMV retinitis treated with intravenous ganciclovir; two patients with CMV retinitis treated with an intravitreal sustained-release ganciclovir device; one patient with CMV retinitis treated with intravenous foscarnet; and two patients with AIDS without CMV retinitis who did not receive any anti-CMV therapy. The paraffin was removed from the sections, and indirect immunofluorescent staining was performed, using an antiserum to ganciclovir.

RESULTS

Bright fluorescent staining was noted in the retinal pigment epithelium (RPE) and photoreceptor outer segments of eyes treated with intravenous or intravitreal ganciclovir, but not in eyes treated with foscarnet or without CMV retinitis. In addition, patches of bright fluorescent staining of the internal limiting membrane was noted in eyes treated with intravitreal ganciclovir.

CONCLUSIONS

Ganciclovir is detected in the outer retina of patients with CMV retinitis treated with intravenous or intravitreal therapy. The drug is detected also in the internal limiting membrane in eyes treated with the intravitreal sustained-release ganciclovir device.

Dopamine transporter density measured by [123I]beta-CIT single-photon emission computed tomography is normal in dopa-responsive dystonia

The clinical distinction between dopa-responsive dystonia (DRD) and juvenile Parkinson's disease JPD) can pose a diagnostic challenge. Both conditions are dopa responsive. However, long-term L-dopa benefit is very different between the two. The difference in the prognosis is due to presence or absence of nigral cell loss. In JPD, there is degenerative nigral cell loss, whereas there are enzymatic defects in dopamine synthesis without cell loss in DRD. Mutations have been found in the GTP cyclohydrolase I (GCH-I) and tyrosine hydroxylase genes in DRD. As the discovered mutations are multiple and more are expected to be found, it is difficult to confirm or exclude DRD by mutation studies. Measurement of cerebrospinal fluid (CSF) neopterin will detect DRD from mutations in the GCH-I gene but not from mutations in tyrosine hydroxylase. The dopamine transporter (DAT) is a protein in the dopaminergic nerve terminals. (1R)-2beta-Carbomethoxy-3beta-(4-[123I]iodophenyl)tropane ([123I]beta-CIT) is a ligand for the DAT, and it was shown to be a useful nuclear imaging marker for neurons that degenerate in Parkinson's disease (PD). As DRD was shown to have a normal DAT without nigral cell loss in a postmortem study, we predicted that the DAT measured in vivo by nuclear imaging will be normal in DRD and will differentiate DRD from JPD. Therefore, we performed [123I]beta-CIT single-photon emission computed tomography ([123I]beta-CIT SPECT) in clinically diagnosed DRD, PD, and JPD, and examined whether DAT imaging can differentiate DRD from PD and JPD. We then examined whether DAT imaging can provide a screening tool for molecular genetic studies, by studying mutations in the candidate gene GCH-I and measuring CSF neopterin. Five females (4 from two families, and 1 sporadic) were diagnosed as DRD based on early-onset foot dystonia and progressive parkinsonism beginning at ages 7 to 12. All patients were functioning normally on L-dopa 100 to 250 mg/day for up to 8 years. SPECT imaging was obtained after intravenous injection of [123I]beta-CIT; 15 healthy volunteers served as normal control, and 6 PD and 1 JPD as disease controls. [123I]beta-CIT striatal binding was normal in DRD, whereas it was markedly decreased in PD and JPD. Gene analysis showed a novel nonsense mutation in the GCH-I gene in one family. No mutation was found in the other family or in the sporadic case. CSF neopterin was markedly decreased in the 4 tested patients. [123I]beta-CIT SPECT is a sensitive method for probing the integrity of nigrostriatal dopaminergic nerve terminals. A normal striatal DAT in a parkinsonian patient is evidence for a nondegenerative cause of parkinsonism and differentiates DRD from JPD. Finding a new mutation in one family and failure to demonstrate mutations in the putative gene in other cases supports the usefulness of DAT imaging in diagnosing DRD.

A simulation of subtractive hybridization

Various strategies employed in genomic DNA cloning by subtractive hybridization have been examined by computer simulations, with the comparison between the predictions and the published results. The result shows that the efficiency of target sequence enrichment and the sensitivity to experimental conditions depend strongly on the enrichment strategy employed. The strategy selecting only tester/tester after hybridization can be very efficient to enrich targets. For successful target enrichment, however, the strategy requires a highly efficient subtraction method and proper hybridization conditions. The strategy also requires that the selected DNA be amplified by polymerase chain reaction (PCR) after each or each alternate subtraction. By contrast, the strategy selecting tester/tester plus single-stranded tester is less sensitive to various experimental factors, compared with the strategy selecting only tester/tester. However, it is not as efficient. With this strategy, the tester DNA selected may or may not be amplified by PCR before the next round. In the case of the strategy selecting single-stranded tester, the target DNA can be successfully enriched only when the selected DNA is directly used without PCR amplification in the next round. The strong features of existing methods can be combined to develop a protocol that is more efficient and more reliable.

Measurement of cell proliferation by labeling of DNA with stable isotope-labeled glucose: studies in vitro, in animals, and in humans

A method for measuring DNA synthesis and, thus, cell proliferation, in vivo is presented. The technique consists of administering [6,6-2H2]Glc or [U-13C]Glc, isolating genomic DNA, hydrolyzing enzymatically to free deoxyribonucleosides, and derivatizing for GC-MS analysis of dA or dG isotopic enrichments, or both. Comparison of dA or dG to extracellular Glc enrichment (with a correction for intracellular dilution) reveals the fraction of newly synthesized DNA, by application of the precursor-product relationship. Thus, the technique differs from the widely used [3H]thymidine or BrdUrd techniques in that the de novo nucleotide synthesis pathway, rather than the nucleoside salvage pathway, is used to label DNA; the deoxyribose rather than the base moiety is labeled; purine rather than pyrimidine deoxyribonucleosides are analyzed; and stable isotopes rather than radioisotopes are used. The method is applied here in vitro to the growth of HepG2 and H9 cells in culture; in animals to proliferation of intestinal epithelium, thymus, and liver; and in humans to granulocyte turnover in blood. In all instances, measured cell proliferation kinetics were consistent with expected or independently measured kinetics. The method has several advantages over previously available techniques for measuring cell turnover, involves no radioactivity or potentially toxic metabolites, and is suitable for use in humans. The availability of a reliable and safe method for measuring cell proliferation in humans opens up a number of fundamental questions to direct experimental testing, including basic problems related to cancer, AIDS, and other pathologic states.

Identification of functionally important residues of human thrombopoietin

Thrombopoietin (TPO) is a megakaryocyte growth and differentiation factor. It consists of a characteristic two domain structure. The amino-terminal domain of TPO has a sequence homology with erythropoietin and is required for the binding and activation of its receptor c-Mpl. To determine the functionally important regions interacting with its receptor, a series of site-directed mutants of TPO were constructed based on a three-dimensional model of the amino-terminal domain. Two strategies of mutagenesis were employed: 1) nonnative N-linked glycosylation scan of 12 residues predicted to be on the surface, and 2) alanine replacement scan of mostly charged 44 amino acid residues. Each TPO mutein was transiently expressed in COS7 cells, and the specific bioactivity of the TPO protein secreted into the culture medium was measured using a recombinant BaF3 cell line expressing human c-Mpl. Four alanine substitutions at Arg10, Pro42, Glu50, and Lys138 nearly or completely abolished the activity, whereas the mutation at Arg14 slightly decreased the activity, suggesting that these residues are functionally important in interacting with its receptor. These residues mapped to helix A, loop AB, and helix D. Sequence comparison between human TPO and other mammalian TPO showed that the identified residues are completely conserved among the species. However, unlike the recent report on the mutational analysis of TPO, alanine substitutions at Lys52, Lys59, Arg136, and Arg140 did not affect the TPO activity significantly in our system. The identified receptor binding regions of TPO are analogous to those of human growth hormone and erythropoietin. Based on the similarity of these three cytokines, we propose that Lys138 of helix D and Pro42 and Glu50 of loop AB may constitute one binding region, whereas Arg10 and Lys14 of helix A may constitute the other binding region to dimerize the receptors.

Purification and properties of phenylalanine ammonia-lyase from leaf mustard

Phenylalanine ammonia-lyase (PAL, EC 4.3.1.5), the first enzyme in phenylpropanoid biosynthesis, catalyzes the elimination of ammonium ion from L-phenylalanine. In the present study, PAL was purified through ammonium sulfate fractionation, DEAE-cellulose chromatography, Sephadex G-200 chromatography, and Q-Sepharose chromatography from the cytosolic fraction of leaf mustard (Brassica juncea var. integrifolia). It consists of 4 subunits, each having an estimated molecular weight of about 40,000 on SDS-polyacrylamide gel electrophoresis (SDS-PAGE). The optimal pH and temperature of the purified enzyme are 9.0 and 45 degrees C, respectively. Its activity is inhibited by Zn2+ ion, and it is strongly activated by caffeic acid. The purified PAL seems to have some characteristics different from those obtained with other PALs.

Ischemia induces significant changes in purine nucleoside concentration in the retina-choroid in rats

Adenosine, produced from the decomposition of adenosine triphosphate, is believed to provide protective effects during ischemia. On the other hand, adenosine metabolites may serve as precursors for oxygen free radical formation. The time course of formation of adenosine and its purine metabolites was studied during retinal ischemia in rats. Concentrations of adenosine and its purine nucleoside metabolites inosine, hypoxanthine, and xanthine in the retina-choroid of ketamine/xylazine-anesthetized rats were measured during retinal ischemia using high performance liquid chromatography. Quantitative measurements were made possible in the small tissue mass through the use of internal standards. Ischemia was induced by ligation of the central retinal artery. In each rat, one eye was ischemic while the other served as a non-ischemic control. Eyes were frozen in situ at 1, 5, 10, 20, 30, 60, and 120 min of ischemia. The retina-choroid was then removed from the frozen eyes and analysed. Significant increases in the concentrations of adenosine, inosine, and hypoxanthine in ischemic compared to control retina-choroid were detectable within 1 to 5 min of the onset of ischemia, and within 10 min for xanthine. Increase in adenosine concentration in ischemic relative to control retina-choroid plateaued at 30 min of ischemia, while inosine and hypoxanthine concentrations increased continuously. The increase in xanthine concentration was exponential throughout the measurement period. This study documented the time-related changes in purine nucleoside concentration during ischemia. Prolonged ischemia results in ongoing production of xanthine, which by serving as a precursor for oxygen free radical formation, could be a pathogenic factor in prolonged retinal ischemia.

Adenosine receptor blockade and nitric oxide synthase inhibition in the retina: impact upon post-ischemic hyperemia and the electroretinogram

We preformed this study to determine the effect on ocular blood flow and the electroretinogram of either nitric oxide synthase (NOS) inhibition, adenosine receptor blockade or the combination of both after 1 hr of ocular ischemia. Thirty-seven cats under general anesthesia were subjected to 1 hr of complete ischemia in one eye by raising the intraocular pressure above systolic blood pressure. The other eye in each animal served as a non-ischemic control. Arterial blood gas tension, systemic arterial pressure, body temperature, hematocrit, and anesthetic level were controlled in each experiment. Cats were divided into four groups. Group 1 received normal saline injections [intravenous (i.v.) and intravitreal], Group 2 adenosine receptor blockade (0.1 ml of 0.01 M 8-sulfophenyltheophylline intravitreal) and saline i.v., Group 3 NOS inhibition (30 mg/kg l-NG-nitroarginine-methyl-ester i.v.) and saline intravitreal, and Group 4 intravitreal adenosine receptor blockade and NOS inhibition i.v. A subset of Group 3 received l-arginine to investigate the reversibility of NOS inhibition, after the blood flow measurements were completed. Five minutes after the end of ischemia, blood flows in retina and choroid were measured using injections of radioactively labeled microspheres. Electroretinographic (ERG) studies were carried out before treatment, before ischemia, during ischemia, and 1, 2, 3, and 4 hr after ischemia ended. NOS inhibition significantly reduced basal blood flow in the choroid, and in the retina when combined with adenosine receptor blockade. Adenosine receptor blockade completely attenuated post-ischemic hyperemia in the retina, but retinal hyperemia reappeared when adenosine receptor blockade and NOS inhibition were combined. Adenosine receptor blockade had no effect on ERG recovery after ischemia. NOS inhibition led to a reduction of ERG a- and b-wave amplitudes in control eyes, that could be reversed by l-arginine. Nitric oxide (NO) appears to be a significant factor in the regulation of basal blood flow in the choroid. Adenosine appears to be a major mediator of retinal hyperemia after 60 min of ischemia. Since NOS inhibition appeared to have direct effects on ERG wave amplitudes, short-term ERG studies may be of limited use in assessing the role of NO in postischemic recovery of the retina. Our observations correlate well with the emerging role of NO as a neurotransmitter in the retina.

The zygomatic-sphenoid fracture line in malar reduction. A cadaver study

OBJECTIVE

To demonstrate the persistent malar displacement and distraction of the zygomatic-sphenoid fracture line that is possible after alignment of the frontozygomatic and infraorbital rim fractures of a displaced malar fracture.

DESIGN

Nonblinded cadaver study.

SUBJECTS

Three fresh cadaver heads and 1 representative clinical example.

INTERVENTION

The cadaver heads were subjected to blunt trauma to the malar eminence. Reduction of the malar unit was performed either with attention to the frontozygomatic and infraorbital rim fractures alone or with concomitant inspection of the zygomatic-sphenoid fracture line. The representative case was repaired with a trans-conjunctival approach for inspection of the zygomatic-sphenoid fracture line.

RESULTS

Persistent malar asymmetry is possible after the reduction of displaced malar fractures when only the frontozygomatic and infraorbital rim buttresses are used for reference. In each case in our study, the zygomatic-sphenoid fracture line remained distracted. Alignment of the zygomatic-sphenoid fracture restored premorbid malar position.

CONCLUSION

Inspection of the zygomatic-sphenoid fracture line can contribute significantly to the precise 3-dimensional reduction of displaced malar fractures.

Effect of chronic administration of alcoholic beverages and seasoning containing alcohol on hepatic ethanol metabolism in mice

Five-week-old male mice, C3H/HeNCrj (C3H/He), were given a 5% (v/v) ethanol solution, commercial alcoholic beverages (Japanese sake (sake) or red wine) or a Japanese seasoning (mirin [containing ethanol and a large amount of glucose]) ad libitum for 45 d, and were then examined for changes in the hepatic enzymes related to ethanol metabolism 2 h after oral administration of 5 g of ethanol/kg body weight. The specific activity of aniline hydroxylase (ANH) in the hepatic microsome increased significantly in all groups chronically administered ethanol solution, sake, red wine or mirin, and the greatest increase was in the hepatic microsome of mirin-administered mice. The cytochrome P-450 (CYP) 2E1 increased in the hepatic microsome of the mice administered ethanol solution, red wine or mirin where accompanied by high ANH activity. The immunoreactive band for CYP1A1 showed high specificity in the microsome of mice given sake, red wine or mirin. It was assumed that CYP1A1 was induced by unknown component(s) other than ethanol in these solutions. In the cytosolic fraction, following the chronic administration of sake and mirin, the total aldehyde dehydrogenase (A1DH) activity with high-Km decreased significantly. In the mitochondrial fraction, the activity of high-Km A1DH increased significantly in the mirin-administered mice which drank a large amount of ethanol, whereas that in the red wine-administered group tended to decrease. These results indicate that the enzyme activities related to the oxidation of both ethanol and acetaldehyde in the cytosolic, mitochondrial and microsomal fractions of the liver were affected by either the action of ethanol or its interaction with other constituents of sake, red wine and mirin.

Isolation and characterization of the cDNA encoding the prophenoloxidase of fall webworm, hyphantria cunea

Two kinds of cDNA clones encoding prophenoloxidases (ProPO; zymogen of phenoloxidase (monophenol, L-dopa: oxygen oxydoreductase, EC 1.14.18.1)) were isolated by polymerase chain reaction (PCR) followed by screening of cDNA library that was prepared from whole larvae of the fall webworm, Hyphantria cunea (Lepidoptera, Arctiidae). The cDNAs encode 681 and 697 amino acids with molecular masses of 78.2 and 80.2 kDa, respectively. Deduced amino acid sequence homology between the two H. cunea ProPOs are only 49% whereas the homology against other insect ProPOs ranged from about 40 to 72%. The phylogenic analysis showed that the insect ProPOs are grouped mainly into two families. A putative proteolytic cleavage site for enzyme activation was identical to other insect ProPOs. The conserved copper binding sites were 84-62% homologous to arthropod ProPOs. Two additional highly conserved regions were found in the carboxy terminal. Furthermore, like other insect prophenoloxidases, hydrophobic signal peptide sequences were absent in the deduced ProPOs from H. cunea. Southern blot analysis indicated that the H. cunea ProPO1 is present as a single copy in the genome. Northern blot analysis showed that the expression of the ProPO genes were concentrated in mid-instar larvae, but were much lower in other developmental stages.

Reconstructive rhinoplasty

Reconstructive rhinoplasty for larger nasal defects requires a three-dimensional perspective using many of the aesthetic and functional techniques commonly employed in rhinoplasty. There are numerous ways of addressing a deficiency of the internal lining and each technique is detailed. Structural grafting is imperative in order to resist the contracture and collapse of the reconstructive nose. These grafts are also used to enhance contour and definition. Resurfacing of large cutaneous defects is frequently achieved through the midline forehead flap. There are many subtle maneuvers which can significantly impact the final aesthetic outcome and these are discussed below. This article highlights the three-layered approach to subtotal and total reconstructive rhinoplasty.

New approaches in clinical chemistry: on-line analyte concentration and microreaction capillary electrophoresis for the determination of drugs, metabolic intermediates, and biopolymers in biological fluids

The use of capillary electrophoresis (CE) for clinically relevant assays is attractive since it often presents many advantages over contemporary methods. The small-diameter tubing that holds the separation medium has led to the development of multicapillary instruments, and simultaneous sample analysis. Furthermore, CE is compatible with a wide range of detectors, including UV-Vis, fluorescence, laser-induced fluorescence, electrochemistry, mass spectrometry, radiometric, and more recently nuclear magnetic resonance, and laser-induced circular dichroism systems. Selection of an appropriate detector can yield highly specific analyte detection with good mass sensitivity. Another attractive feature of CE is the low consumption of sample and reagents. However, it is paradoxical that this advantage also leads to severe limitation, namely poor concentration sensitivity. Often high analyte concentrations are required in order to have injection of sufficient material for detection. In this regard, a series of devices that are broadly termed 'analyte concentrators' have been developed for analyte preconcentration on-line with the CE capillary. These devices have been used primarily for non-specific analyte preconcentration using packing material of the C18 type. Alternatively, the use of very specific antibody-containing cartridges and enzyme-immobilized microreactors have been demonstrated. In the current report, we review the likely impact of the technology of capillary electrophoresis and the role of the CE analyte concentrator-microreactor on the analysis of biomolecules, present on complex matrices, in a clinical laboratory. Specific examples of the direct analysis of physiologically-derived fluids and microdialysates are presented, and a personal view of the future of CE in the clinical environment is given.

Concentrations of adenosine and its metabolites in the rat retina/choroid during reperfusion after ischemia

PURPOSE

Little is known about the nature of biochemical disturbances during reperfusion after retinal ischemia. Previous studies have suggested that adenosine is responsible for regulation of retinal blood flow soon after ischemia has ended. Therefore, in this study we measured concentrations of adenosine and its metabolites in the rat retina/choroid after brief (10 min) or prolonged (60 min) periods of ischemia, and the functional consequences of inhibiting adenosine metabolism.

METHODS

Ischemia was produced in anesthetized rats by ligation of the central retinal artery. The eyes were frozen in situ and purine nucleoside concentration was determined by high performance liquid chromatography. The functional effects of pre-ischemic inhibition of xanthine dehydrogenase/xanthine oxidase were assessed by measurement of the electroretinogram before, during, and up to 7 days following 60 min ischemia.

RESULTS

Changes in the concentrations of adenosine and its metabolites were significant early in the reperfusion period, and were greater in magnitude and occurred earlier in prolonged, compared to brief, ischemic periods. Concentrations of adenosine, inosine, and hypoxanthine remained elevated for 30 min following the end of 60 min ischemia, and xanthine concentration was significantly elevated until 60 min after the end of either 10 or 60 min of ischemia. The onset of its peak value after ischemia was delayed in comparison to that of adenosine. Ischemia-evoked increases in xanthine concentration were attenuated by inhibition of adenosine deaminase or xanthine oxidase/xanthine dehydrogenase. Pre-ischemic inhibition of xanthine oxidase/xanthine dehydrogenase by oxypurinol (40 or 80 mg/kg intraperitoneally [IP]) resulted in a significant improvement in recovery of the a and b waves of the electroretinogram in comparison to a saline-treated control group.

CONCLUSIONS

These results indicate that adenosine is a major component of the biochemical changes that occur after retinal ischemia. Long-lasting increases in xanthine concentration during reperfusion after ischemia could be a source of oxygen free radicals that may contribute to delayed injury of the retina, attempts to decrease xanthine concentration would ideally be initiated within one hour after the end of ischemia.

Protein purification and cDNA cloning of a cecropin-like peptide from the larvae of fall webworm (Hyphantria cunea)

A proteinous antimicrobial substance was purified from the bacteria-challenged larvae of the fall webworm, Hyphantria cunea. It is a cecropin-like antibacterial peptide which exhibits antibacterial activity against Gram-negative and Gram-positive bacteria, and known as Hyphantria cecropin A. The cDNA clones corresponding to this peptide were isolated from a cDNA library constructed from the bacteria-challenged larvae and obtained complete nucleotide sequences. In addition to the Hyphantria cecropin A sequence, we obtained three other cDNAs exhibiting high sequence similarity with Hyphantria cecropin A. We synthesized the C-terminally amidated peptide of 35 residues based on the deduced sequence of the isolated cDNA of Hyphantria cecropin A. The synthetic peptide exhibited strong antibacterial activity against several microbes including medically important bacteria such as Salmonella, Shigella, and fungus such as Candida. A Southern blot experiment using these cloned cDNAs as probes predicted the existence of multiple forms of Hyphantria cecropin genes.

Pollen tube guidance by the female gametophyte

In flowering plants, pollen grains germinate on the pistil and send pollen tubes down the transmitting tract toward ovules. Previous genetic studies suggested that the ovule is responsible for long-range pollen tube guidance during the last phase of a pollen tube's journey to the female gametes. It was not possible, however, to unambiguously identify the signaling cells within an ovule: the haploid female gametophyte or the diploid sporophytic cells. In an effort to distinguish genetically between these two possibilities, we have used a reciprocal chromosomal translocation to generate flowers wherein approximately half the ovules do not contain a functional female gametophyte but all ovules contain genotypically normal sporophytic cells. In these flowers, pollen tubes are guided to the normal but not to the abnormal female gametophytes. These results strongly suggest that the female gametophyte is responsible for pollen tube guidance, but leave open the possibility that the gametophyte may accomplish this indirectly through its influence on some sporophytic cells.

Primary structure of 6.5k-arginine/glutamate-rich polypeptide from the seeds of sponge gourd (Luffa cylindrica)

The amino acid sequence of 6.5k-arginine/glutamate rich polypeptide (6.5k-AGRP) from the seeds of sponge gourd (Luffa cylindrica) has been determined. The 6.5k-AGRP consists of a 47-residue polypeptide chain containing two disulfide bonds, and a molecular mass calculated to be 5695 Da, which fully coincides with a value of [M+H]+ = m/zeta 5693.39 obtained by matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS). The mass spectrometric evidence indicated that 6.5k-AGRP is also present partially truncated at the C-terminus. In our preparations, approximately half of the polypeptide molecules have the C-terminal sequence Arg-Arg-Glu-Val-Asp; the other half lack Val-Asp and end with the glutamic acid, making a total of 45 residues in the polypeptide chain. The two disulfide bonds connect Cys12 to Cys33 and Cys16 to Cys29. Comparison of the amino acid sequence of 6.5k-AGRP with those of the other known proteins included in the PIR protein sequence database showed that it is related to the amino acid sequence of the N-terminal region encoded by the first exon of the cocoa (Theobroma cacao) and cotton seeds vicilin genes, sharing a characteristic two Cys-Xaa-Xaa-Xaa-Cys motif.