Stability of thrombosis induced by electrocoagulation of rat middle cerebral artery

BACKGROUND AND PURPOSE

Although it is often assumed in experimental stroke studies that cautery-induced occlusion is permanent, surgeons commonly expect cauterized vessels to recanalize spontaneously. We used the rat middle cerebral artery to determine if electrocoagulation would produce a permanent occlusion in this preparation.

METHODS AND RESULTS

A standard bipolar coagulator, calibrated to determine actual power output, was adjusted to induce platelet aggregation in the middle cerebral artery of anesthetized Sprague-Dawley rats without inducing bleeding through the arterial wall. A reliable temporary thrombosis was induced by a Malis Bipolar Coagulator set to deliver 10 bursts of 1.5 seconds each at a rate of 24 min-1 and a power setting of 3 W. This thrombus was responsive to the antithrombotic agent flunarizine. An apparently permanent occlusion was produced by 30 bursts at 3 W followed by 20 bursts at 5 W. To our surprise, seven of seven such occlusions recanalized spontaneously within 4 hours.

CONCLUSIONS

The electrocoagulation process commonly used in experimental stroke studies may produce only a temporary occlusion of the rat middle cerebral artery.

Ammine/amine platinum (II) complexes effective in vivo against murine tumors sensitive or resistant to cisplatin and tetraplatin

Three homologous series, each differing from the other in the coordinated amine ligand class, namely alicyclic, heterocyclic or isoaliphatic, were highly effective against wild-type murine leukemia L1210/0 cells in vivo (T/C = 171%-426% at optimal doses). Of the 13 complexes comprising the three series, 3 were inactive in the cisplatin-resistant L1210/DDP model, but the other 10 maintained good efficacy (T/C = 131%-167%). Long-term survivors, frequently observed with these complexes in the L1210/0 model, were also seen in the L1210/DDP model but to a lesser extent. In the homologous alicyclic series, which contained six analogs, as the alicyclic ring size increased, potency against L1210/0 and L1210/DDP cells also increased up to cyclohexylamine, and then declined. Four ammine/alicyclic amine analogs were evaluated against L1210/DACH cells, which are cross-resistant to tetraplatin, and the clinically predictive M5076 reticulosarcoma. Although the congeners were ineffective or minimally effective in prolonging the survival time of L1210/DACH-bearing mice (T/C = 111%-134%), 20%-40% cure rate was consistently observed and suggested that the compounds possessed a low inherent ability to circumvent resistance in these tumor cells also. In the solid M5076 model, activity was greatest (tumor growth delays of about 25 days) for the alicyclic homologs containing the ammine/cyclobutylamine or ammine/cyclopentylamine carrier ligand combination. In summary, ammine/amine platinum (II) analogs have demonstrated promise at the preclinical level in their ability to circumvent acquired resistance, which is a major drawback of cisplatin use in treating cancer.

[Therapy of experimental autoimmune myasthenia gravis in rabbits with 4-aminopyridine and 3,4-diaminopyridine]

The autoimmune myasthenia gravis (AMG) in rabbits was produced by intradermal injection of N-AChR-rich membrane vesicles isolated from the electric organ of Narcine limlei. After i.v. 4-aminopyridine (4-AP) 0.8 mg.kg-1 to 8 AMG rabbits, their general posture improved promptly, the features of gastrocnemius compound action potentials and toe twitches elicited by 4-Hz stimuli applied to the sciatic nerve returned to normal, and the tetanic plateau evoked by 50-Hz indirect stimulation was again well sustained. This improved condition lasted 9.1 +/- 2.5 h. Other 8 AMG rabbits given 3,4-diaminopyridine (3,4-DAP) 0.4 mg.kg-1 showed a similar improvement for 9.3 +/- 3.1 h. These results indicated that 4-AP and 3,4-DAP were effective in treating the AMG in rabbits, they may be useful in the clinical treatment of myasthenia gravis patients.

Evidence that cell toxicity may contribute to the genotoxic response

Comparisons of the structural determinants associated with genotoxic effects with those associated with cell or systemic toxicity indicate extensive overlaps. These findings can be taken to indicate that toxicity may contribute to genotoxicity.

Structural basis of the induction of unscheduled DNA synthesis in rat hepatocytes

The structural basis of the induction of unscheduled DNA synthesis (UDS) in isolated rat hepatocytes was studied with CASE, an expert system. The analysis identified a number of structural determinants associated with the induction of UDS. These structures accounted for 97.3% of the activity of the chemicals in the database. Further analyses indicated that the concordance between prediction and experimentally determined UDS of molecules not in the learning set is > 82%. A comparison of predictions of UDS and mutagenicity in Salmonella indicated that there is a dichotomy between these activities. The basis of this lack of coincidence remains to be elucidated.

Kinetics of tissue disposition of cis-ammine/cyclohexylamine-dichloroplatinum(II) and cisplatin in mice bearing FSaIIC tumors

The clinical potential of mixed amine platinum(IV) complexes has been identified, and interest in this new class of antitumor agents has been heightened by demonstration of their activity in cisplatin-resistant neoplasms. These tetravalent platinum agents are expected to undergo a reductive reaction to form the corresponding platinum(II) drug prior to eliciting biological activity. cis-Ammine/cyclohexylamine-dichloroplatinum(II) is one such product that we evaluated with cisplatin in vivo, and we found the two complexes given i.v. or i.p. to have comparable activities against a solid murine fibrosarcoma. Following i.v. administration of the two compounds at equitoxic dose levels (20 mg/kg) to tumor-bearing mice, platinum levels in the plasma were consistently higher for cisplatin. Tissue platinum levels, in contrast, were comparable between the agents or higher for the mixed amine analog at the earliest (3-h) time point. The temporal profiles determined for the concentrations over 48 h were tissue- and/or drug-specific and could be described by terminal-phase constants or half-lives of platinum in most tissues. In the plasma, kidney, lung, and jejunum, platinum levels arising from both compounds decayed with half-lives of 24-92 h. The terminal-phase constants of platinum determined in the heart for the two complexes were not significantly different from zero, indicative of levels remaining steady, whereas the constants were negative in the spleen, indicative of an increase in tissue drug concentration. In the tumor, liver, and testes, positive values for the decay-phase constants corresponding to half-lives of 47, 256, and 79 h, respectively, were seen with the mixed amine complex; this pattern contrasted with that found for cisplatin, for which the terminal-phase constant was either zero or negative. In vitro binding studies demonstrated the mixed amine complex to be more reactive. Thus, the presence of one ammine and one cyclohexylamine carrier ligand in the mixed amine complex, as opposed to the diammine ligands in cisplatin, leads to an increase in drug distribution and an alteration in the kinetics of tissue binding and removal of platinum.

Adaptive response to mutagenesis and its molecular basis in a human T-cell leukemia line primed with a low dose of gamma-rays

The effect was studied of a low dose of gamma-ray preexposure on the frequency and molecular spectrum of radiation-induced mutations at the hprt locus in a human T-cell leukemia line. When the cells were preexposed to 0.01 Gy of gamma-rays, the yield of mutations induced by a subsequent 2-Gy challenge dose was reduced by 60%, compared with the 2 Gy of irradiation alone. The data of Southern blot analysis showed that 47% of the mutants induced by 2 Gy in the cells without low-dose preexposure were of the deletion or rearranged mutations type. In contrast, in the low-dose radioadapted cells the proportion of this type of 2-Gy-induced mutations decreased to 28%. This is close to the control level (22%) of spontaneous mutations. Our results confirm that a low dose of gamma-ray preexposure leads to a decreased susceptibility to gene deletions and rearrangements after high-dose irradiation.

[Specific curative effects of nitrosourea drugs on tumor cells with Mer--phenotype in Chinese]

O6-Methylguanine DNA methyltransferase (O6-MT) activity and cellular sensitivity to nitrosourea drugs of 10 kinds of tumor cell strains derived from Chinese patients were measured by 3H radioactivity and colony-forming ability, respectively. The results in vitro showed that nimustine (Nim) 25 micrograms.ml-1 and carmustine (Car) 20 micrograms.ml-1 exhibited specific killing effects on Mer-phenotype tumor cells characterized by low O6-MT activity. In vivo both Nim and Car (25 mg.kg-1.wk-1 x 4 wk, ip) had specific curative ability to Mer- tumor cells implanted in nude mice. These findings suggested that assay of O6- MT activity in tumor biopsy could be used as a predictable guide to human tumor chemotherapy with nitrosourea compounds.

Mitochondrial DNA sequence evolution in the Arctoidea

Some taxa in the superfamily Arctoidea, such as the giant panda and the lesser panda, have presented puzzles to taxonomists. In the present study, approximately 397 bases of the cytochrome b gene, 364 bases of the 12S rRNA gene, and 74 bases of the tRNA(Thr) and tRNA(Pro) genes from the giant panda, lesser panda, kinkajou, raccoon, coatimundi, and all species of the Ursidae were sequenced. The high transition/transversion ratios in cytochrome b and RNA genes prior to saturation suggest that the presumed transition bias may represent a trend for some mammalian lineages rather than strictly a primate phenomenon. Transversions in the 12S rRNA gene accumulate in arctoids at about half the rate reported for artiodactyls. Different arctoid lineages evolve at different rates: the kinkajou, a procyonid, evolves the fastest, 1.7-1.9 times faster than the slowest lineage that comprises the spectacled and polar bears. Generation-time effect can only partially explain the different rates of nucleotide substitution in arctoids. Our results based on parsimony analysis show that the giant panda is more closely related to bears than to the lesser panda; the lesser panda is neither closely related to bears nor to the New World procyonids. The kinkajou, raccoon, and coatimundi diverged from each other very early, even though they group together. The polar bear is closely related to the spectacled bear, and they began to diverge from a common mitochondrial ancestor approximately 2 million years ago. Relationships of the remaining five bear species are derived.

Development of a method to assess the informational content of structure-activity data bases

The ability to predict the biological or toxicological properties of yet untested chemicals based upon structure-activity relationships (SAR) is very dependent upon the size and chemical diversity of the "learning set" used to develop the SAR model. In the present study it is shown that for noncongeneric chemicals, systematically increasing the informational contents of "learning sets" by iteratively selecting chemicals based upon structural diversity increases the predictivity of the SAR model. This approach can now be used to generate learning sets with maximal informational content while keeping the number of chemicals that require testing at a minimum.

[Oro-pharyngeal flora in severely burned patients]

Throat cultures were taken in thirty-seven cases of burned patients, and also, at the same time, from twenty-three healthy persons. The results showed that the essential oro-pharyngeal flora in healthy persons were Neisseria (65.7%) and Streptococcus viridans (14.3%), and Staphylococcus aureus was obtained occasionally. In twenty-five out of thirty-seven patients dominant growth of invaders was observed. The prominent aerobic bacteria in patients included Serratia (9.33%), Pseudomonas aeruginosa (8.44%) and Proteus (7.11%). The positive rate of fungi was as high as 75.1%, of which Candida was the most commonly found organism. In 7 patients the number of bacteria in the throat was in excess of 108/cm2. Of these 7 patients, 4 died. Quantitative bacterial count of lungs were taken in 3 non-survivors, and the bacterial count was over 10(5)/g. The bacteria in the lungs were as same as the predominantly colonized bacteria in the throat, and in a part of cases were the same as the systemically disseminated bacteria. The study of the throat flora is simple, its result might help the prediction of pulmonary infection.

Anesthetic effects on motor evoked potentials in dogs

The effects of the various anesthetic agents on the production of transcranial magnetic motor evoked potentials (tcMMEP) were studied in a canine model. Pre-anesthetic baseline tcMMEPs demonstrated consistency in onset latency measurements and variability in measurement of peak-to-peak amplitudes. Changes in tcMMEPs were evaluated following the individual administrations of sodium pentothal, etomidate, halothane, fentanyl, and ketamine. For induction of anesthesia, etomidate was compatible with tcMMEP production, whereas sodium pentothal resulted in loss of hindlimb potentials for a period of 45 minutes. For maintenance of anesthesia, halothane was incompatible with the measurement of tcMMEPs. Fentanyl administration was consistent with the recording of reliable tcMMEPs, with consistent onset latencies but widely variable peak-to-peak amplitudes. Ketamine was compatible with stable and reproducible tcMMEP production. The results of this study suggest that anesthetic agents have a predictable and consistent effect on tcMMEP responses.

Weaning practices and growth in rural Sichuan infants: a positive deviance study

To understand some of the factors involved in weaning and growth faltering in rural China, a cross-sectional positive deviance study was undertaken among 389 rural 4-12-month-old infants from two townships of a county in Sichuan. The infants' mothers were interviewed about their child-feeding practices and other sociodemographic information, and anthropometric measurements were made on their infants. Positive deviant infants (those growing adequately in environments in which the majority of the children suffer from growth retardation and malnutrition) were identified from the Chinese WAZ-scores calculated from the anthropometric measurements. Feeding practices found to be associated with the better growth of the positive deviant infants included breastfeeding through age 12 months, feeding soybean milk, liver and pork blood products on a more than weekly basis during the ages of 7-9 months, not feeding rice flour (mifen) before age 7 months, and not giving supplements or tonics. Mothers' nutrition knowledge was also associated with positive deviance status. The relevance of the findings is discussed with respect to designing nutrition education interventions for rural Sichuan.

An approach for evaluating and increasing the informational content of mutagenicity and clastogenicity data bases

A method is described for using the fragments identified by the CASE structure-activity relational expert system to identify the type of chemicals that require further testing in mutagenicity and clastogenicity assays. Inclusion of such chemicals will increase the informational content of databases with respect to structural features that are under-represented in currently available data bases. The method is applied to existing databases (mutagenicity in Salmonella, chromosomal aberrations in Chinese hamster ovary cells, unscheduled DNA synthesis in rat hepatocytes, in vivo induction of micronuclei, somatic mutations in Drosophila melanogaster) to identify structural determinants that are absent.

Modulation of O6-methylguanine-DNA methyltransferase-mediated 1-(4-amino-2-methyl-5-pyrimidinyl) methyl-3-(2-chloroethyl)-3-nitrosourea resistance by O6-benzylguanine in vitro and in vivo

Our previous studies have indicated that O6-methyl-guanine-DNA methyltransferase (MGMT) is a key factor determining tumor cellular resistance to 1-(4-amino-2-methyl-5-pyrimidinyl) methyl-3-(2-chloroethyl)-3-nitrosourea (ACNU). This study describes the modulation of MGMT-mediated ACNU resistance by O6-benzylguanine pretreatment. The ACNU sensitivity of MGMT proficient human tumor HeLa S3, SMMC-7721, and Cc801 cells in tissue culture was markly enhanced by 10 mm O6-benzylguanine, and a correlation between the extent of enhancement and the level of MGMT activities was observed. A single i.p. injection of 100 mg/kg of O6-benzylguanine caused a complete inhibition of MGMT activities in HeLa S3 tumor xenografts and combination of O6-benzylguanine with ACNU (7.5 mg/kg) significantly inhibited HeLa S3 tumor growth. The results demonstrated that O6-benzylguanine could be used as a potential adjuvant in combination chemotherapy with ACNU to treat MGMT proficient tumors.

Depletion of O6-methylguanine-DNA methyltransferase and potentiation of 1,3-bis(2-chloroethyl)-1-nitrosourea antitumor activity by O6-benzylguanine in vitro

The overcoming effect of O6-benzylguanine on O6-methylguanine-DNA methyltransferase (MGMT)-mediated 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) resistance in vitro was evaluated. Depletion of MGMT activity in Mer+ HeLa S3 cells by O6-benzylguanine was dose-dependent and a complete loss of MGMT activity was achieved at a concentration of 0.5 microM. The cytotoxic potential of BCNU on MGMT proficient HeLa S3 (1.10 pmol/mg of protein), SMMC-7721 (0.72 pmol/mg of protein) and Cc801 (0.39 pmol/mg of protein) was greatly enhanced when cells were exposed to 10 microM O6-benzylguanine for 1 h, but there was a lack of potentiation of BCNU sensitivity in Mer- HeLa MR cells due to its nearly undetectable level of MGMT. There existed a correlation between the extent of enhancement and the amount of MGMT activity. The intensity of enhancement expressed as dose modifying factor = IC50 (BCNU alone)/IC50 (10 microM O6-benzylguanine + BCNU) was 4.56, 3.89, 3.67 and 0.97 in HeLa S3, SMMC-7721, Cc801 and HeLa MR cells respectively. The results further demonstrated that O6-benzylguanine may have potential utility as an adjuvant in combination chemotherapy with chloroethylnitrosourea agents.

O6-methylguanine-DNA methyltransferase and human cancer chemotherapy

Two kinds of human tumor cell strains having different activity of O6-methylguanine-DNA methyltransferase (O6-MT) were transplanted into nude mice. Mice were then injected intraperitoneally (i.p.) with the bifunctional agent 1-(4-amino-2-methyl-5-pyrimidinyl) methyl-3-(2-chloroethyl)-3-nitrosourea hydrochloride(ACNU). The tumors with low O6-MT activity were quickly suppressed or cured. This result suggests that some tumors, if determined to have low O6-MT activity, might be cured if the host is treated with ACNU. This observation may open a new approach to experimental cancer chemotherapy. Treatment with ACNU of experimental animals bearing HeLaMR tumors (which have low O6-MT activity and are Mer-), resulted in the regression of the tumors or their disappearance. In animals bearing HeLaS3 tumors (which have high O6-MT activity and are Mer+) the tumors were hyperplastic.

Cultured mouse SR-1 cells exposed to low dose of gamma-rays become less susceptible to the induction of mutagenesis by radiation as well as bleomycin

The effect of pre-exposure of cultured mouse SR-1 cells to a low dose of gamma-rays on the induction of mutations at the hprt locus by subsequent high dose radiation or bleomycin was studied. When cells were pre-exposed to 0.01 Gy gamma-rays, the induction of mutations by a 3 Gy gamma-ray dose given 18 or 24 h later was significantly reduced as compared with those which did not receive the low dose pre-exposure. When cells were challenged with 5 or 10 micrograms/ml bleomycin for 12 h, which can produce double-strand breaks in DNA, instead of 3 Gy gamma-rays, a similar mutagenetic adaptive response was observed. We conclude that this resistance to radiation- or bleomycin-induced mutation is attributed to the induction of a DNA double-strand break repair mechanism.

Phylogenetic relationships of macaques as inferred from restriction endonuclease analysis of mitochondrial DNA

Mitochondrial DNAs (mtDNAs) purified from 25 samples of 6 species of macaques, Macaca mulatta, M. fascicularis, M. arctoides, M. nemestrina, M. assamensis and M. thibetana, were analyzed to study the phyletic relationships among the species. A total of 36-46 sites was observed in each sample. By combining the cleavage patterns for each of the endonucleases, the 25 samples were classified into 11 restriction types. When data on M. fuscata and M. cyclopis collected by other authors were added to our own, the resultant molecular phylogenetic trees indicated that the 8 species may be divided into 4 groups: (1) M. mulatta, M. fuscata, M. cyclopis and M. fascicularis; (2) M. arctoides; (3) M. nemestrina; (4) M. assamensis and M. thibetana. Our results suggest that within both the fascicularis and sinica groups genetic distances are small between members and that the status of the species within the groups may require further investigation.

Cariogenic potential of pooled plaque fluid from exposed root surfaces in humans

The composition of pooled plaque fluid from exposed root surfaces of five population samples was determined before and at selected times (3, 7 and 15 min) after a 5 and 10% sucrose rinse. Subjects were 45-65 yr old, had exposed, sound root surfaces, and were grouped according to root caries status [caries-free (CF), no root caries history; caries-positive (CP), recorded root caries experience]. Samples were obtained only from the sound surfaces of the CF and CP subjects after overnight fasting. Plaque samples from each subgroup were pooled under mineral oil and maintained on ice. Plaque fluid was then isolated by centrifugation and analysed for organic acids and inorganic ions (ion chromatography), and pH (microelectrodes). From these data, the degree of saturation [DS(TM)] in plaque fluid with respect to tooth mineral (TM) was calculated. Before exposure to sucrose, plaque fluids from the CF and the CP subgroups had similar ionic compositions. These fluids were also found to be supersaturated with respect to tooth mineral. After exposure to sucrose, a rapid decrease in plaque fluid pH was observed, which corresponded primarily to lactic acid production. For all times examined, mean pH and DS(TM) values were lower and lactic acid concentrations were higher in the CP than the CF samples. Lower values of DS(TM) suggest that plaque fluid from CP subjects had a measurably greater cariogenic potential. Calcium concentrations also increased significantly and to comparable levels in all plaque fluid samples after sucrose exposure, despite lower acid production in CF samples.(ABSTRACT TRUNCATED AT 250 WORDS)

[Esophageal cancer treated by intracavity radiotherapy with 131I combined with Chinese herbs]

106 patients with esophageal cancer were treated by intracavity radiotherapy with 131I combined with Chinese herbs. The ages ranged from 34-84 years with an average of 59.8 years. All cases were confirmed by cytology and/or pathology. According to the length of lesions the patients were divided into 4 groups: < 3 cm: 1 case; 3-5 cm: 30 cases; 5-7 cm: 37 cases and 7-9 cm: 38 cases. A special three-channel rubber tube were designed. The central tube linked up with a rubber balloon which contained Na131I solution (50 mCi/20 ml) for intracavity radiation. The radiation doses (19653 rads) were delivered continuously to esophageal lesions within 10 days. The Chinese herbs "203" powder and nutrient liquid meal were given separately through the feeding tube and herbs treatment tube. The results showed that 33 cases had complete response, 73 had partial response. The 1 year survival rate was 26/47 (55.3%). 131I combined with Chinese herbs therapy is a promising method for treatment of advanced esophageal cancer.

[A survey of nutrition knowledge-attitudes-practices of Sichuan urban and rural adults]

To provide a basis for designing nutrition education, two nutrition knowledge--attitudes--practices (KAP) surveys of adults aged 18 to 55 were conducted in 1989 in an urban (N = 1004) and a rural (N = 506) area of Sichuan. The results indicated that the nutrition levels in both sites were low, and an awareness of the relationship between nutrition and certain common diseases was lacking. However, both urban and rural adults possessed good attitudes toward nutrition and nutrition education. Large differences existed between urban and rural adults' food patterns, with the rural diet more monotonous than the urban one. The rural women will be a hard-to-reach audience requiring more intensive efforts. The findings suggest that nutrition education efforts for Sichuan urban and rural area adults will require different contents and emphases, different methods of delivery, and language suitable for each group, in order to obtain good results.

Effect of sucrose concentration on the cariogenic potential of pooled plaque fluid from caries-free and caries-positive individuals

Pooled plaque samples were obtained from (1) coronal surfaces of two groups of caries-free (CF) subjects, (2) coronal 'white-spot' surface areas of a group of caries-positive (CP) subjects, and (3) exposed, sound root surfaces of root caries-free (RCF) and root caries-positive (RCP) subjects. The plaque samples were obtained before and 3 min after a 1 min rinse with a 0.5, 1, 2, 5 and 10% sucrose solution. Plaque fluid was then isolated from each plaque sample by centrifugation and analyzed for inorganic ions, organic acids, and pH values. With increasing sucrose concentration: (1) plaque fluid pH and the degree of saturation (DS) with respect to tooth mineral decreased; (2) the pH and DS values of CP and RCP samples were consistently lower than those of CF and RCF samples, respectively; (3) plaque fluid lactic acid concentrations increased and were consistently higher in the CP and RCP samples than in the CF and RCF samples, respectively, and (4) plaque fluid lactic acid concentrations leveled off between 1 and 5% sucrose; this occurred at lower sucrose concentrations with CP and RCP samples than with CF and RCF samples, respectively. RCP samples contained consistently higher levels of mutants streptococci than RCF samples. The chemical composition of plaque fluids, following sucrose exposure, were found to correlate well with caries history. The observed differences in lactic acid concentrations in samples from CF and CP subjects are discussed with regard to differences in microbiological composition and possible differences in plaque permeability to sucrose.

Structural basis of the mutagenicity of heterocyclic amines formed during the cooking processes

A data base consisting of 61 heterocyclic amines formed during food preparation and their des-amino analogs were subjected to structure-activity analysis using the CASE method, a structural activity relational expert system. The program identified the major structural determinants associated with mutagenic activity or lack thereof. The structures identified as contributing to the probability of activity as well as those associated with mutagenic potency were highly predictive of molecules not in the learning set. The major structural determinant, the aromatic amino moiety, and quantum mechanical calculations revealed that the mutagenic potency associated with this functionality derived from their contribution to the energy of the Lowest Unoccupied Molecular Orbital (LUMO).

[Analysis of clinical effect and experimental study of 13 herbs anti-cough-dyspnea decoction in the treatment of chronic bronchitis]

In treating chronic bronchitis, the effect of 13 Herbs Anti-Cough-Dyspnea decoction was better than that of other traditional prescriptions such as Ephedria-almond decoction etc. The effective rate of this decoction in relieving cough, sputum, bronchial spasm and eliminating wheezing sound were 98.6%, 98.32%, 91.52% and 85.35% respectively. The total effective rate was 98%. The animal experiment revealed that the decoction was given to isolated trachea after medication for 30 min, the effective rate in easing bronchial spasm was 99.1 +/- 30.2%, which was two times than that of other prescriptions.

FTIR spectroscopic studies of the conformation and amide hydrogen exchange of a peptide model of the hydrophobic transmembrane alpha-helices of membrane proteins

The conformation and amide hydrogen exchangeability of the hydrophobic peptide Lys2-Gly-Leu24-Lys2-Ala-amide were studied by Fourier transform infrared spectroscopy. In these studies information on the secondary structure of the peptide was obtained from an examination of the contours of both the amide I and amide II absorption bands. The conformationally sensitive amide I and amide II regions of the infrared spectra suggest that the peptide is predominantly alpha-helical and that it contains some non-alpha-helical structures which are probably in an extended conformation. Studies of the exchangeability of the amide protons of the peptide indicate that there are two populations of amide protons which differ markedly with respect to their exchangeability with the bulk solvent phase, whether the peptide is dissolved in methanol or dispersed in hydrated lipid bilayers. One population of amide protons is very readily exchangeable, and our data suggest that it arises primarily but not exclusively from the extended regions of the peptide. The other population exchanges very slowly with the bulk solvent and appears to originate entirely from the alpha-helical domain of the peptide. This latter population is virtually unexchangeable when the peptide is dispersed in hydrated phosphatidylcholine bilayers but can be largely exchanged when the peptide is solubilized with methanol. We suggest that this slowly exchanging population of amide protons arises from the central part of the hydrophobic polyleucine core which forms a very stable alpha-helix that would be deeply buried in the hydrophobic domain of hydrated lipid bilayers.(ABSTRACT TRUNCATED AT 250 WORDS)

Interaction of a peptide model of a hydrophobic transmembrane alpha-helical segment of a membrane protein with phosphatidylcholine bilayers: differential scanning calorimetric and FTIR spectroscopic studies

High-sensitivity differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy were used to study the interaction of a synthetic model hydrophobic peptide, Lys2-Gly-Leu24-Lys2-Ala-amide, and members of the homologous series of n-saturated diacylphosphatidylcholines. In the low range of peptide mole fractions, the DSC thermograms exhibited by the lipid/peptide mixtures are resolvable into two components. One of these components is fairly narrow, highly cooperative, and exhibits properties which are similar to but not identical with those of the pure lipid. In addition, the fractional contribution of this component to the total enthalpy change, the peak transition temperature, and cooperativity decrease with an increase in peptide concentration, more or less independently of acyl chain length. The other component is very broad and predominates in the high range of peptide concentration. These two components have been assigned to the chain-melting phase transitions of populations of bulk lipid and peptide-associated lipid, respectively. Moreover, when the mean hydrophobic thickness of the PC bilayer is less than the peptide hydrophobic length, the peptide-associated lipid melts at higher temperatures than does the bulk lipid and vice versa. In addition, the chain-melting enthalpy of the broad endotherm does not decrease to zero even at high peptide concentrations, suggesting that this peptide reduces but do not abolish the cooperative gel/liquid-crystalline phase transition of the lipids with which it is in contact. Our DSC results indicate that the width of the phase transition observed at high peptide concentration is inversely but discontinuously related to hydrocarbon chain length and that gel phase immiscibility occurs when the hydrophobic thickness of the bilayer greatly exceeds the hydrophobic length of the peptide. The FTIR spectroscopic data indicate that the peptide forms a very stable alpha-helix under all of our experimental conditions but that small distortions of its alpha-helical conformation are induced in response to any mismatch between peptide hydrophobic length and bilayer hydrophobic thickness. These results also indicate that the peptide alters the conformational disposition of the acyl chains in contact with it and that the resultant conformational changes in the lipid hydrocarbon chains tend to minimize the extent of mismatch of peptide hydrophobic length and bilayer hydrophobic thickness.

[Effect of injection of enkephalin and bestatin in caudate-putamen on operant conditioning in rats]

Female Wistar rats were trained in a Skinner-box, 30 trials per day in a dark room to establish operant defence conditioning. Training started with a light (15 s), then combined with footshock for further 8 s. When the rats learned to press the key to avoid footshock within 15 s, conditioned response was considered established. After the rats reached a conditioning rate (CR) above 80% for 5 days, cannulae were implanted into caudate-putamen. Two to three days later, Met-enkephalin (MEK) or bestatin (an aminopeptidase inhibitor) was injected bilaterally into caudate-putamen. 30 min, 2 h, 24 h and 48 h after injection, conditioning tests were conducted, with each session consisting of 30 trials. Control experiments were done when 0.9% NaCl (NS) was injected. After injection of NS, CR maintained above 80% in all 4 test sessions. MEK (60 ng/rat) or bestatin (10 micrograms/rat) significantly lowered the CR during the 30 min and 2 h test session. In the latter case, the latency (L) was also prolonged. However both CR and L returned to the control level in the 24 h and 48 h test sessions. Naloxone (2 mg/kg, i.p.) blocked the conditioning-depression effect of bestatin. No significant alteration was seen in locomotor activity after MEK or bestatin injection. The results suggest that enkephalin in caudate-putamen may be involved in the regulation of retrieval of conditioning. Bestatin mimics the effect of MEK on conditioning reflex probably by increasing production of endogenous enkephalin.

Delayed-nonmatching-to-sample performance is impaired by extensive, but not by limited, lesions of the thalamus in the rat

Two experiments were conducted to determine whether lesions affecting limited areas of the thalamus can impair the performance of rats on a spatial delayed-nonmatching-to-sample (DNMTS) task trained before surgery. In Experiment 1, DNMTS was not affected by lesions produced by injecting 5 microliters of 1 mM N-methyl-D-aspartate into either the midline thalamus (n = 16) or bilaterally 1.0 mm from the midline (n = 16). In experiment 2, radio-frequency lesions were made 1.0 mm lateral to the midline at 3 anterior-posterior locations that destroyed the full rostral-caudal extent of the lateral internal medullary lamina (L-IML; n = 8), or at single anterior-posterior locations that destroyed either the anterior (n = 8) or posterior (n = 8) portions of the L-IML site. Although complete L-IML lesions disrupted DNMTS performance to an extent comparable to that of another study (Mair & Lacourse, 1992), lesions that were restricted to either the anterior or posterior portion of the L-IML site had no significant effect on this task.

O6-methylguanine-DNA methyltransferase activity in human tumors

The distribution of O6-methylguanine-DNA methyltransferase (MGMT) activity in extracts of tumors from 74 patients was measured. The results demonstrated that there was considerable variation of MGMT activity in different human tumor tissues as well as in different individuals. The mean values (X +/- SD, pmol/mg of protein) in breast cancer, stomach cancer, small cell lung cancer, non-small cell lung cancer, renal cell carcinoma, esophageal carcinoma, brain tumors, colon carcinoma and malignant melanoma were 1.071 +/- 0.374 (9), 0.515 +/- 0.107 (5), 0.509 +/- 0.251 (5), 0.461 +/- 0.227 (24), 0.329 +/- 0.246 (5), 0.273 +/- 0.376 (5), 0.244 +/- 0.175 (14), 0.242 +/- 0.308 (5) and 0.201 +/- 0.161 (2) respectively. It was notable that six samples (1/24 non-small cell lung cancer, 3/5 esophageal carcinoma, 1/14 brain tumors and 1/5 colon carcinoma) did not have any detectable level of MGMT activity. Activity of glutamine pyruvic transaminase (GPT) was also measured in the same extracts used for the assay of MGMT activity. The activity of GPT in these samples with undetectable level of MGMT activity was similar to those with significant MGMT activity. These results further strengthen the assumption that a certain fraction of human tumors are Mer-.

LEU2 gene homolog in Kluyveromyces lactis

A DNA fragment that can complement the leu2 mutation of Saccharomyces cerevisiae was cloned from the genomic library of Kluyveromyces lactis. The nucleotide sequence revealed an open reading frame of 362 codons, 75% homologous to S. cerevisiae LEU2 gene. The upstream region contained a CCGGAACCGG sequence identical to the site of leucine-specific control of LEU2. Further upstream, there is a partial open reading frame homologous to rat ribosomal protein L7.

Transformation of the gram-positive bacterium Clavibacter xyli subsp. cynodontis by electroporation with plasmids from the IncP incompatibility group

We report the transformation of a gram-positive bacterium, Clavibacter xyli subsp. cynodontis, with several plasmids in the IncP incompatibility group from gram-negative bacteria. Our results suggest that IncP plasmids may be transferable to other gram-positive organisms. After optimizing electroporation parameters, we obtained a maximum of 2 x 10(5) transformants per microgram of DNA. The availability of a transformation system for this bacteria will facilitate its use in indirectly expressing beneficial traits in plants.

[Amphetamine--induced rage reaction in mice and its mechanism]

Rage reaction was induced in mice by ip amphetamine sulfate (APT) 15 mg/kg. Mice appeared hyperreactive after 6 min and then squeaked and fought each other. These manifestations were most distinct in 15-30 min and subsided after 40-70 min. At 20 degrees C and 25 degrees C, the occurrence of rage reaction was 85.0% and 90.0% respectively. The ED50 of APT for eliciting rage reaction was 11.8 +/- 2.1 mg/kg ip. No significant difference in the induction of rage reaction was observed between male and female mice but ambient temperature affected the occurrence of this reaction. Neuroleptic drugs (chlorpromazine, haloperidol, tardan and clozapine), anxiolytic drugs (diazepam and meprobamate) and reserpine suppressed the rage reaction induced by APT in mice. Phenobarbital and pentobarbital (at sedative doses), atropine, scopolamine, phentolamine and propranolol exerted no influence on APT--induced rage reaction. Amantadine, levodopa and apomorphine at lower doses potentiated the rage inducing effect of APT. Moreover, at higher doses amantadine or levodopa alone also evoked rage reaction similar to that induced by APT. Therefore, it may be deduced that the APT-induced rage reaction results from increased release of dopamine in limbic system and has nothing to do with the simultaneous epinephrine release. The available data indicate that the APT--induced rage reaction in mice deserves to be recommended as an animal model for screening potential neuroleptic drugs. The merits and shortcomings of this new model are discussed.

Delayed-nonmatching-to-sample performance is impaired by extensive, but not by limited, lesions of the thalamus in the rat

Two experiments were conducted to determine whether lesions affecting limited areas of the thalamus can impair the performance of rats on a spatial delayed-nonmatching-to-sample (DNMTS) task trained before surgery. In Experiment 1, DNMTS was not affected by lesions produced by injecting 5 microliters of 1 mM N-methyl-D-aspartate into either the midline thalamus (n = 16) or bilaterally 1.0 mm from the midline (n = 16). In experiment 2, radio-frequency lesions were made 1.0 mm lateral to the midline at 3 anterior-posterior locations that destroyed the full rostral-caudal extent of the lateral internal medullary lamina (L-IML; n = 8), or at single anterior-posterior locations that destroyed either the anterior (n = 8) or posterior (n = 8) portions of the L-IML site. Although complete L-IML lesions disrupted DNMTS performance to an extent comparable to that of another study (Mair & Lacourse, 1992), lesions that were restricted to either the anterior or posterior portion of the L-IML site had no significant effect on this task.

A convenient method of measuring the thermal conductivity of biological tissue

The basic principle of the thermal conductivity probe is described. Thin probes were developed based on this principle, with a reproducibility of 5.3% and relative error less than 6.0%. Each measurement can be completed in 90 s and the temperature increase can be controlled within 2 degrees C. Using the probes, the thermal conductivities of pig fat, meat, liver, kidney and live and dead snake head were measured and it was found that water content plays an important role in influencing the magnitude of the thermal conductivity of biological tissues. The probe can be used over a temperature range from -40 to 150 degrees C.

Genetic diversity in the Chinese pangolin (Manis pentadactyla): inferred from restriction enzyme analysis of mitochondrial DNAs

Two different forms of Chinese pangolins can be recognized according to the color of their scales, i.e., brown and dusky. We analyzed mitochondrial DNA (mtDNA) purified from the livers of seven dusky and six brown Chinese pangolins from the same locality, using cleavage patterns from 19 restriction enzymes. From the 19 6-bp recognition enzymes used, 51-56 sites were observed. By combining the cleavage patterns for each enzyme, the 13 samples were classified into four restriction types: two in dusky and two in brown Chinese pangolins. The estimated number of nucleotide substitutions per site in dusky and brown types is 0.002, and that between dusky and brown types is 0.012. Divergence between brown and dusky forms began 0.6 Myr ago, provided the mean rate of sequence divergence is 0.02 per Myr in mtDNA. Our results suggest that there is considerable divergence in Chinese pangolins, and brown and dusky Chinese pangolins may be quite different forms or, at least, belong to different maternal groups.

Implications of newly recognized relationships between mutagenicity, genotoxicity and carcinogenicity of molecules

The CASE structure-activity relational method was used to predict the mutagenicity, cytogenotoxicity, carcinogenicity, sensory irritation, male rat-specific alpha 2 mu-nephrotoxicity and maximum tolerated dose of a population of molecules (N greater than or equal to 1300). These chemicals were then sorted out by their predicted responses to specific tests and sub-populations of molecules with different prevalence with respect to described endpoints were constructed, i.e. 0-100% prevalences of mutagens, rodent carcinogens and SCE inducers. The predicted properties of these populations were analyzed and the overlap among tests was determined. The method also permits the determination of the dependence among assays and the level of false-positive and false-negative predictions.

Designing appropriate nutrition education for the Chinese: the urban and rural nutrition situation in Sichuan

In the People's Republic of China, as in the West, diet has emerged as an important determinant of morbidity and mortality. In order to provide one of the bases for designing nutrition education, two nutrition knowledge-attitudes-practices surveys of adults aged 18-55 were conducted in 1989 in an urban (N = 1004) and a rural (N = 506) area of Sichuan. Nutrition knowledge levels were low in both sites, but lower in the rural site. Certain general nutrition concepts, such as the value of a varied diet, were reported correctly by over 50 per cent of the population in both areas. However, less than 10 per cent of the urban residents and only 3 per cent of the rural residents reported taking correct measures to prevent or delay cancer or heart disease. Dietary practices, elicited by a food frequency questionnaire, revealed large differences in consumption habits in the two areas. More than half of the urban respondents reported eating rice, vegetable oil, green vegetables, lean meat, and wheat on a daily basis, and other vegetables, pickles, fruit, eggs, soybean products, and meat fat on at least a weekly basis. However, the rural respondents reported eating only rice, vegetable oil, green vegetables, and other vegetables on a daily basis, and no additional foods on a weekly basis.(ABSTRACT TRUNCATED AT 250 WORDS)

[Common pathogens in burn infection and changes in their drug sensitivity]

This paper reports common pathogens in burn infection and changes in their drug sensitivity from 1985 to 1988. Gram negative rods constituted 55.7% of all pathogens, while 40.5% were gram positive cocci. The former group consisted of 173 strains of Pseudomonas aeruginosa (28.5%), 55 Proteus (9.1%), 33 Serratia (5.4%), 23 Klebsiella (3.8%) 19, Acinetobacter (3.1%), 18 Enterobacter (3.0%) and 17 E. coli (2.8%). Among gram-positive cocci, Staphylococcus aureus accounted for 32.8%, Staphylococcus epidermidis accounted for 5.6%, and Streptococcus faecalis accounted for 2.1%. All the gram-negative rods and gram-positive cocci showed more resistance against various antibiotics. Ps. aeruginosa were resistant to 24 commonly used antibiotics. However, ciprofloxacin, ceftaztdime and piperacillin were comparatively effective, the sensitivity rates were 92.9%, 91.5% and 78.3%, respectively. Ps. aeruginosa showed a sensitivity rate of 92.5% and 86.1% to amikacin and polymyxin-B, respectively, from 1980 to 1984, but the rates were lowered to 65.9% and 17.3%, respectively, from 1985 to 1988. Staphylococcus aureus showed a sensitivity rate of 88.9% to ciprofloxacin, 76.1% to ceftazidime, 71.4% to amikacin, 48.5% to piperacillin, 63.1% to cefuroxime. This organism showed a sensitivity rate of 87.3%, 83.9%, 81.7% and 82.8% to amikacin, cefoperozone, leucomycin and lincomycin, respectively, from 1980 to 1984, but the sensitivity rates declined to 71.4%, 56.8%, 60.8% and 43.7%, respectively, from 1985 to 1988.

O6-methylguanine-DNA methyltransferase and human cancer chemotherapy

Two kinds of human tumor cell strains having different activity of O6-methylguanine-DNA methyltransferase (O6-MT) were transplanted into nude mice. Then the mice were injected intraperitoneally with bifunctional alkylating agent 1-(4-amino-2-methyl-5-pyrimidinyl) methyl-3-(2-chloroethyl)-3-nitrosourea hydrochloride (ACNU). The tumors with low O6-MT activity were quickly suppressed or cured. The result suggests that some tumors, if provisionally determined with low O6-MT activity, might be efficiently cured by treatment with ACNU. This probably opens a new way for human cancer chemotherapy.

Conformational transition of fructose-1,6-bisphosphatase: structure comparison between the AMP complex (T form) and the fructose 6-phosphate complex (R form)

A structure of the neutral form of fructose-1,6-bisphosphatase complexed with AMP has been determined by the molecular replacement method and refined at a 2.5-A resolution to a crystallographic R factor of 0.169. The root-mean-square errors of the structure from standard geometry are 0.013 A for bond lengths and 2.99 degrees for bond angles. Comparison of the AMP complex with the F6P complex shows that dimer C3-C4 twists about 19 degrees about a molecular 2-fold axis when dimers C1-C2 of the R and T forms of the enzyme are superimposed one another and that a slight shift of about 1 A of the AMP domain partially compensates this twist. The R to T transition of the enzyme does not significantly change the conformation of the F6P-binding site. However, residues at the divalent metal site and the AMP site show significant positional shifts. If these results can be extended to substrate in place of F6P, they suggest that regulation of the enzyme by AMP may occur partly through effects on metal-ion affinity or position. AMP binds to the same sites of the T and R forms, but only half-occupancy was observed in the alkaline R form. Sequential binding of AMP, at least in pairs, is suggested as the unligated R form is converted to the T form. Two possible pathways are suggested for allosteric communication over about 28 A between the AMP site and the active site: one via helices H1, H2, and H3 and another via the eight-stranded beta-sheet.(ABSTRACT TRUNCATED AT 250 WORDS)

Crystal structure of the neutral form of fructose-1,6-bisphosphatase complexed with the product fructose 6-phosphate at 2.1-A resolution

The crystal structure of fructose-1,6-bisphosphatase (EC 3.1.3.11) complexed with the product fructose 6-phosphate (F6P) has been refined at 2.1-A resolution to an R factor of 0.177 with root-mean-square deviations of 0.014 A and 2.9 degrees from the ideal geometries of bond lengths and bond angles, respectively. The secondary structures but not the trace of the unligated enzyme have been slightly revised in the F6P complex at this higher resolution. Helix H4 in the unligated structure has been refined to a helix-like coil, and two very short 3(10) helices have been found, one in H4 and one in H5. F6P at 10 mM concentration in the absence of divalent metals in our study shows major binding at the active site and minor binding at the AMP site. The major site has almost equal full occupancy in the C1 and C2 chains of the crystallographic asymmetric unit, while the minor site shows occupancy only in the C1 chain at about 50%. The electron density in both (2Fo - Fc) and (Fo - Fc) maps calculated by omitting F6P slightly favors the beta anomer of D-F6P over the alpha anomer. Possible functions of the active-site residues are discussed, and candidates are suggested for site-directed mutagenesis.

Determination of eight elements in six human cancer cell lines and two human normal cell lines by PIXE

Gastric, hepatic, and pulmonary cancer cell lines, and the third passage of normal gastric and pulmonary cell lines were analyzed by proton induced X-ray emission (PIXE) method. The contents of element Sr, Ca, Fe, Zn, P, K, Cu, and As in the cell lines were determined. The Sr, Ca, Fe, Zn, and As contents in cancer cell lines were significantly lower than those in the normal cell lines (p less than 0.05), whereas there were no significant differences for the P, K, and Cu contents (p greater than 0.1). The results suggest that the need of some essential elements has been diminished in cancer cell proliferation.

[Anaerobic infection of burns]

To analyze anaerobic infection 158 specimens were obtained from deep necrotic tissues and exudates under burned subeschar, secretion of eyes and blood. The results showed that more anaerobes were isolated from deep necrotic tissues (46.88%) and smelly exudates of subeschar (38.71%). Most of them were mixed with aerobes (97.1%). In 43 strains of anaerobes, Clostridium accounted for 18 strains (41.86%), and Bacteroides for 17 strains (39.53%). Fusiform nucleatum. Peptococcus, and Veillonell paryula were also differentiated. The recent total detectable rate of anaerobes (38.71%) from burn wounds was higher significantly than that of 1980-1983 (14.7%). It may be due to the exact selection of specimens and modification of cultural medium and equipment.

[Parenteral magnesium sulfate exerts no central anticonvulsant action]

It was said that parenteral magnesium (MS) had a central anticonvulsant action responsible for controlling seizures in eclampsia of pregnancy. The present study was carried out to examine this statement. In conscious rabbits, MS 214 mg.kg-1 iv quickly relieved them from convulsion induced by sc pentylenetetrazol, yet spikes of high frequency in electrocorticogram burst inceasingly. Judging from electrocorticogram changes, MS 220 mg.kg-1 iv did not raise the electroshock seizure threshold. In mice, MS 430 mg.kg-1 did not significantly increase the LD50 of ip pentylenetetrazol. However, in anesthetized rats, MS 250 mg.kg-1 ip lowered the hypertensive response to angiotensin amide and norepinephrine. These results indicated that parenterally administered MS exerted no demonstrable central anticonvulsant action, and its benefits gained in the treatment of eclampsia of pregnancy might derive from its peripheral action, such as reduction of vascular response to pressor substances.

Embryotoxicity and teratogenicity of DL111-IT, an early pregnancy-terminating agent, in the subsequent gestation following administration in rats

DL 111-IT is a new non-hormonal early pregnancy-terminating agent. The subsequent embryotoxic and teratogenic effects of DL111-IT were studied in the rats whose first pregnancy had been terminated by the agent. The secondary pregnancy of the treated rats were allowed to initiate at 30-, 45-, and 90-day intervals, respectively, after the termination of the first pregnancy. The toxicities primed with DL111-IT, such as resorbed embryos and nephrohydrosis fetuses, were found to be 8.0% and 8.5%, respectively, in the rats with pregnancy at 30-day interval. This is significantly different from 4.0% resorbed embryos and 2.4% nephrohydrosis fetuses in vehicle control (P less than 0.05). However, the rate of resorbed embryos decreased to 7.0% or 6.0% in the rats with pregnancy at 45- or 90-day intervals, respectively. No other significant embryotoxicity and teratogenicity were observed in those rats initiating their pregnancy 45 days later after first-pregnancy termination by DL111-IT. Thus, DL111-IT appears to have very low subsequent toxicity in the course of rat pregnancy cycles.

[4-aminopyridine induced rage reaction in mice]

Rage reaction was induced in mice by sc 4-aminopyridine (4-AP) 6 mg . kg-1. Mice appeared hyperreactive after 8-12 min and then squeaked and fought each other. These manifestations were most distinct in 10-30 min and subsided after 40-60 min. The occurrence of rage reaction on this dose level was around 90%. At higher doses 4-AP caused convulsions and death after evocation of rage reaction. The ED50 of 4-AP for eliciting rage reaction was 4.7 +/- 0.7 mg . kg-1 sc. No significant difference in induction of rage reaction was seen between male and female mice of different body weights. Both neuroleptic drugs (chlorpromazine, haloperidol, tarden and clozapine) and anxiolytic drugs (diazepam, chlordiazepoxide, and meprobamate) inhibited 4-AP-induced rage reaction in mice. Barbiturates, Chloral hydrate, methaqualone, morphine hydrochloride, aspirin, phenytoin sodium, diphenhydramine hydrochloride, atropine sulfate, and procaine hydrochloride did not affect rage reaction. The 4-AP-induced aggressive behavior, similar to that induced by electric footshock or isolation, has the merits of convenience to deal with and time saving. Hence we recommended it as a screening method for drugs with neuroleptic and anxiolytic activities.

The termini of the chlorella virus PBCV-1 genome are identical 2.2-kbp inverted repeats

The Chlorella virus PBCV-1 genome is a linear nonpermuted 333-kbp dsDNA molecule with covalently closed hairpin termini. The termini (minus the hairpin) are identical inverted repeats of at least 2185 bases after which the sequence diverges. The inverted repeats contain two small potential open reading frames and several direct repeats. However, neither the open reading frames nor the remainder of the inverted repeats are transcribed during PBCV-1 replication. Twenty-nine other Chlorella virus DNAs, of 36 tested, hybridized to the PBCV-1 terminal fragments.