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Biomedical subjects

Z Yu

Publications and source records attributed to Z Yu.

At least 343 records · Page 19Linked to original sources
PubMed1994

Impact of acid and pepsin on human esophageal prostaglandins.

OBJECTIVES: Although the prostaglandin-mediated mucosal protection within the gastric compartment has been well established, its potential role in the maintenance of integrity of the esophageal mucosa in humans has not been explored due to the lack of appropriate methodology. METHODS: We have recently developed an esophageal perfusion catheter, equipped with two balloons, compartmentalizing a 7.5-cm segment of the esophageal lumen. Using this catheter, we studied the impact of the luminal perfusion with saline, HCl (0.01 M, pH 2.1), and HCl/pepsin solutions (0.5 mg/ml) on esophageal luminal release of PGE2 in 21 asymptomatic, presumably healthy volunteers (12 M, 9F; mean age 40 yr). The content of PGE2 in its methyl oximated form was measured by RIA (Amersham, IL), using a novel iodinated label. Results are expressed as mean +/- SEM. Student's t test was used for statistical analysis. RESULTS: Perfusion of the esophageal lumen resulted in continuous release of PGE2 into the perfusate at the rate of 1880 +/- 393 pg/min during the first 8-min perfusion period. During continuation of perfusion with saline, the luminal release of PGE2 was maintained at the rate of 1820 +/- 640 pg/min during the second 8-min perfusion period. This rate declined (although in nonsignificant fashion; p < 0.2) during the third perfusion period, reaching a plateau of 1220 +/- 473 pg/min and maintained during the last (period IV) perfusion period with saline. Introduction of acid during the perfusion period II in the second group of investigated subjects resulted in a rapid and statistically significant decline of the luminal release of PGE2 to the value of 1020 +/- 167 ng/min (p < 0.01). Continuation of esophageal perfusion with acid during the next 8-min perfusion period further diminished the luminal release of PGE2 to the value of 520 +/- 73; p < 0.001. The significant decline in the rate of luminal PGE2 release was still maintained despite the replacement of acid with saline during the ending 8-min perfusion (period IV; 560 +/- 80 ng/min; p < 0.001). Esophageal perfusion with HCl/pepsin solution, in group III subjects, potentiated luminal release of PGE2, reaching the value of 1553 +/- 340 pg/min, which is 3 times higher than the value of PGE2 observed during corresponding perfusion with HCl (period III; p < 0.03). This significant impact of HCl/pepsin solution was still maintained despite the substitution of HCl/pepsin with NaCl during the last perfusion period, and was still significantly higher (1260 +/- 220 pg/min; p < 0.02) than the corresponding value during the ending perfusion with NaCl after HCl (group II). This study for the first time demonstrates that luminal release of PGE2 in humans remains under a significant impact of luminal chemical factors such as acid and pepsin. CONCLUSION: The modulatory effect of acid and pepsin on esophageal mucosal prostaglandin release may play a role in the development of reflux-related mucosal pathology.

Adult↗
PubMed1994

Impairment of salivary epidermal growth factor secretory response to esophageal mechanical and chemical stimulation in patients with reflux esophagitis.

OBJECTIVES: It has been demonstrated recently that salivary epidermal growth factor (sEGF) output in healthy individuals is strongly and significantly influenced by esophageal intraluminal mechanical and chemical stimuli. Therefore, we have studied the impact of intraesophageal mechanical and chemical stressors on the rate of secretion of sEGF in 14 patients with reflux esophagitis (RE), and compared these results with corresponding parameters measured in 14 sex- and age-matched controls. METHODS: EGF was assessed in saliva collected during basal conditions, chewing of parafilm, placement of esophageal tubing, inflation of intraesophageal balloons, and perfusion with NaCl, HCl, and HCl/pepsin solutions. The concentration of sEGF was measured with an RIA kit from Amersham (Arlington Heights, IL). RESULTS: The concentrations of sEGF were (mean +/- SEM) 2.50 +/- 0.32 ng/ml and 2.00 +/- 0.37 ng/ml in basal saliva and during stimulation by chewing the parafilm, respectively. Basal sEGF value appeared to be significantly higher than in controls (2.50 +/- 0.32 vs. 1.90 +/- 0.22 ng/ml, p < 0.05, in one-tailed t test). Placement of intraesophageal tubing resulted in a significant decline of sEGF concentration, compared with parafilm-stimulated conditions (1.25 +/- 0.12 vs. 2.00 +/- 0.37 ng/ml, p < 0.0001) and corresponding tubing-stimulated sEGF value in controls (1.25 +/- 0.12 vs. 1.52 +/- 0.16 ng/ml, p < 0.05). sEGF concentrations after inflation of intraesophageal balloons and subsequent perfusion with initial saline, HCl, HCl/pepsin, and ending saline were also highly significantly lower (1.05 +/- 0.18 ng/ml, p < 0.001; 1.10 +/- 0.20 ng/ml, p < 0.001; 1.10 +/- 0.18 ng/ml, p < 0.001; 1.10 +/- 0.19 ng/ml, p < 0.001; and 1.05 +/- 0.18 ng/ml, p < 0.001, respectively) than sEGF concentration recorded during stimulation with parafilm. Concentrations of sEGF during esophageal perfusion with HCl, HCl/pepsin, and ending saline were also significantly lower than corresponding values in controls (1.10 +/- 0.18 vs. 1.49 +/- 0.11 ng/ml, p < 0.05; 1.10 +/- 0.19 vs. 1.59 +/- 0.11 ng/ml, p < 0.05; and 1.05 +/- 0.18 vs. 1.65 +/- 0.13 ng/ml, p < 0.01, respectively). The rate of sEGF output, which was 1.30 +/- 0.24 ng/min during basal conditions, increased significantly during stimulation with parafilm (2.30 +/- 0.38 ng/min, p < 0.05). Both basal and parafilm-stimulated sEGF outputs were somewhat higher, although nonsignificantly, than corresponding values recorded in healthy individuals. Mechanical and chemical stimulation (initial NaCl, HCl, and ending NaCl) failed to evoke a significant increase in sEGF output over the value observed during parafilm stimulation in patients with RE, although such a significant increase was clearly demonstrated in healthy individuals. Therefore, sEGF output in patients with RE remained significantly lower than corresponding values recorded in controls during an entire mechanical stimulation (2.65 +/- 0.35 vs. 4.60 +/- 0.85 ng/min, p < 0.001, after placement of intraesophageal tubing and 2.80 +/- 0.54 vs. 5.15 +/- 0.70 ng/min, p < 0.001, after inflation of balloons). sEGF output in patients with RE remained also significantly lower than adequate control values during chemical stimulation (3.65 +/- 0.64 vs. 5.20 +/- 0.60 ng/min, p < 0.05, during perfusion with initial saline; 3.70 +/- 0.70 vs. 5.20 +/- 0.60 ng/min, p < 0.05, during perfusion with HCl; 3.70 +/- 0.52 vs. 5.55 +/- 0.72 ng/min, p < 0.01, during perfusion with HCl/pepsin, and 3.30 +/- 0.56 vs. 5.80 +/- 0.86 ng/min, p < 0.001, during ending saline). CONCLUSION: Impairment in sEGF secretion during mechanical and chemical intraesophageal stimulation, mimicking the natural scenario occurring during gastroesophageal reflux, may facilitate the development of esophageal mucosal pathology and delay the healing of already developed mucosal injury.

Adult↗
PubMed1993

The nitrogenase proteins of Rhizobium meliloti: purification and properties of the MoFe and Fe components.

The alfalfa-Rhizobium meliloti symbiosis contributes a major portion of biologically fixed nitrogen to temperate zone forage crop production. Highly-purified molybdenum-iron (MoFe) and iron (Fe) nitrogenase components were obtained for the first time from extracts of R. meliloti bacteroids. Intact bacteroid cells were isolated anaerobically from 100 g quantities of alfalfa nodules following storage in liquid nitrogen. Centrifuged bacteroid extracts showed a marked reduction in specific activity when assayed at protein concentrations less than 1 mg/ml. Both nitrogenase proteins were resolved and purified to homogeneity as determined spectroscopically and by SDS-PAGE. The purified MoFe protein differed in several respects from previously characterized nitrogenase proteins. Saturation of the acetylene-reducing and proton-reducing activities of the R. meliloti MoFe protein required higher relative concentrations of Fe protein than nitrogenase proteins purified from free living diazotrophs. Electron allocation to dinitrogen reduction was sustained at component ratios similar to those present in bacteroid extracts, suggesting that while the observed saturation effects were not detrimental to physiological function in the symbiotic system, overall activity could be enhanced by higher levels of iron protein. Analyses of the MoFe protein gave 22 Fe, 22 labile sulfide and 1.7 Mo atoms per molecular unit of 215 kDa. Dithionite-reduced MoFe protein contained a spin 3/2 iron centre but had a lower visible absorbance at 360 nm than the equivalent Azotobacter chroococcum component. Amino-acid composition indicated a notably lesser tryptophan content, and cysteine content greater than that of the equivalent tetrameric protein of free living diazotrophs. Ratios of acidic and basic residues were similar to other MoFe proteins. Calculation of hydrophobicity and discriminant parameters gave values midway between those expected for soluble cytoplasmic proteins and peripheral membrane associated proteins. ADP was tightly bound by the dithionite-free MoFe protein containing reduced iron-molybdenum cofactor. The R. meliloti iron protein was found to be a 64 kDa homodimer containing a single 4Fe-4S metal centre.

Amino Acids↗
PubMed1993

Circadian rhythm in aspirin (ASA)-induced injury to the stomach of the fasted rat.

Circadian rhythms exist in several gastric parameters affecting ulcerogenesis. This study investigated possible circadian rhythmicity in observed aspirin (ASA)-induced gastric lesions in the rat. In five experiments 183 rats were studied at 14 time points over a 24-hr period. Rats were adapted for three weeks on a 12-hr light schedule, fasted 18 hr, then given oral acidified ASA. One hour later, the rats were sacrificed, the stomachs were removed, stretched flat, photographed, scanned, and measured for percent area of gross lesions in the gastric corpus by computer planimetry. Cosinor rhythmometric analysis showed a significant (P < 0.001) rhythm. Mean of rhythm (MESOR) was 5.60 +/- 0.25% of total corpus. Amplitude was 25.89 +/- 6.07% of MESOR. Peak time (acrophase) was 1909 +/- 0101 hr after lights on. Thus, gastric vulnerability to ASA injury exhibited circadian rhythmicity with peak injury during the dark period in this species.

Animals↗
PubMed1993

Compressive and diametral tensile strengths of current adhesive luting agents.

Strength parameters greatly influence the selection of luting agents. This study compared the compressive and diametral tensile strengths of six classes of new adhesive luting agents (ALAs) with zinc phosphate as the controls. The 11 materials tested were prepared according to the manufacturers' instructions for use as luting agents. Mean compressive and diametral strengths and standard errors were calculated for each luting agent (n = 10). Analysis of variance was computed (p < 0.0011) and multiple comparisons tests were performed. Compressive strengths varied from 41.5 MPa for a hydroxyapatite ALA to 178.5 MPa for a composite resin ALA. Diametral tensile strengths ranged from 8.1 MPa for a hydroxyapatite ALA to 45.1 MPa for a composite resin ALA. Conventional powder-liquid glass ionomer ALAs, an encapsulated glass ionomer ALA, a composite resin-glass ionomer hybrid ALA, and the composite resin ALAs demonstrated significantly greater compressive and diametral strengths than the zinc phosphate cements.

Analysis of Variance↗
PubMed1993

Elevated endometrial natural killer cell activity during early porcine pregnancy is conceptus-mediated.

This study investigated an extended time course of endometrial NK cell activity during gestation and the mechanisms underlying changes in uterine NK cell activity in pigs. Endometrial tissues were collected from cyclic, pseudopregnant and pregnant nulliparous pigs on various days post-estrus, and from pigs 10 days after insemination with seminal plasma or killed spermatozoa. NK effector cells were isolated from each endometrial sample, size fractionated and tested for cytolytic activity against NK target cells (K562) using chromium release assays and immunocytochemically for the frequency of perforin-positive cells. Various cell fractions showed different levels of NK activity and had different proportions of cells expressing perforin. Morphologically, cells in the fraction with maximal NK activity almost all showed typical lymphocyte size and shape. Substantially elevated NK cell activity was recorded in pregnant pigs on days 10 and 20 of gestation. By day 30, the cytolytic activity declined dramatically to an almost undetectable level. Very little activity was found in uterine cells isolated from cyclic, pseudopregnant, and seminal plasma or killed spermatozoa inseminated animals, and no differences were detected either between follicular and luteal phases of the estrous cycle or between different days of pseudopregnancy. These results indicate that elevated NK cell activity during early porcine pregnancy cannot be attributed to contributions from either the maternal systemic endocrine status or from components of boar semen. The changes in NK cell activity observed in porcine endometrial tissues during early pregnancy must therefore be associated with the actual presence of conceptuses.

Animals↗
PubMed1993

Effect of esophageal intraluminal mechanical and chemical stressors on salivary epidermal growth factor in humans.

Although various animal and clinical studies have demonstrated the significant effect of salivary epidermal growth factor (sEGF) on esophageal morphology and function, its secretory patterns still remain inadequately explored. Therefore, we have studied the impact of esophageal mechanical and chemical stimuli on sEGF in humans. sEGF was measured in saliva collected during basal conditions, chewing of parafilm, placement of esophageal tubing, inflation of intraesophageal balloons, and perfusion with NaCl, HCl, and HCl/pepsin solutions. The concentration of sEGF was measured with a radioimmunoassay kit from Amersham (Arlington Heights, IL). The concentration of sEGF in basal saliva was (mean +/- SEM) 2.08 +/- 0.22 ng/ml. Chewing the parafilm resulted in a significant decline of sEGF concentration to the value of 1.39 +/- 0.16 ng/ml (p < 0.0005). Similar decline in sEGF concentration also prevailed after placement of intraesophageal tubing (p < 0.03), and inflation of intraesophageal balloons (p < 0.01). This decline intensified significantly when prolonged esophageal perfusion with saline was implemented (p < 0.03 vs. tubing). Substitution of NaCl with HCl in the second and third perfusion periods prevented the decline in sEGF concentration, whereas HCl accompanied by pepsin enhanced sEGF concentration. The rate of sEGF output was 0.90 +/- 0.13 ng/min during basal conditions and increased significantly during parafilm chewing (1.53 +/- 0.25 ng/min; p < 0.05). However, sEGF secretion during both placement of esophageal tubing and inflation of balloons increased 4.1- and 4.9-fold, respectively (p < 0.002 and < 0.00005), over the basal value, and 2.4- and 2.9-fold, respectively, over the parafilm stimulated secretion. Subsequently, we observed a further significant decline of sEGF output (p < 0.05) which was sustained during perfusion of the esophagus with saline. Interestingly, esophageal perfusion with HCl prevented the decline of sEGF secretion observed during perfusion with saline. sEGF output during esophageal perfusion with HCl/pepsin exhibited a strong increase, reaching the value of 5.86 +/- 0.70 ng/ml. This value corresponds to a 58% increase over the secretory rate observed during mechanical stimulation by placement of esophageal tubing (3.71 +/- 0.47; p < 0.05). HCl/pepsin-induced potentiation of sEGF secretion was also highly significantly increased over both the value recorded during basal (p < 0.0005) and parafilm-stimulated (p < 0.002) conditions. Subsequent substitution of HCl/pepsin solution with a final saline perfusate still maintained enhanced sEGF output, compared with both basal (p < 0.02) and parafilm-stimulated conditions (p < 0.02).(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1993

Chemically-modified tetracycline normalizes collagen metabolism in diabetic rats: a dose-response study.

An earlier study indicated that a chemically-modified non-antimicrobial tetracycline (4-de-dimethylaminotetracycline; CMT-1) can inhibit excess collagenase activity in the connective tissues of diabetic rats, however, the optimum oral dose and resulting serum concentration were not determined. In the current study, adult male Sprague-Dawley rats (body weight approx. 350 g) were made diabetic by streptozotocin injection and administered by oral gavage either 0, 1, 2, 5, or 10 mg CMT-1 per day. After 3 weeks of drug therapy, the rats were killed and gingiva, skin, and serum collected. The tissues were 1) extracted, partially purified and analyzed for collagenase activity using [3H-methyl] collagen as substrate and SDS-PAGE/fluorography; 2) extracted in neutral salt and dilute acid solutions (4 degrees C) to assess collagen solubility; and 3) analyzed for hydroxyproline to determine tissue (skin) collagen mass. Serum was analyzed for glucose and CMT-1 concentration, the latter by HPLC. Inducing diabetes dramatically increased both gingival and skin collagenase activity and reduced skin collagen mass by 69.8%. Increasing the oral dose of CMT-1 progressively increased the serum concentration of the drug from 0.6-6.5 micrograms/ml and progressively decreased the excessive collagenase activity in gingiva and skin (p < 0.01 vs untreated diabetics). Although skin collagen mass tended to be increased at all oral doses of CMT-1, only the 5 mg dose effect was statistically significant (p < 0.01). The diabetes-induced reduction in collagen solubility, a classic abnormality (reflecting excessive collagen crosslinking) of this disease, was also normalized by CMT-1 therapy.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1993

Evidence on secretion of epidermal growth factor by the esophageal mucosa in humans.

Luminal release of esophageal epidermal growth factor (EGF) into the perfusing solutions (saline, HCl, and HCl/pepsin), aspirated with the newly developed esophageal perfusion catheter, was measured in 20 healthy volunteers (12 male, 8 female; mean age 40 yr; range 30-56 yr). A potential salivary contamination was excluded by a complete seal (with two balloons) of perfused esophageal segment and by a simultaneous, carefully monitored, collection of saliva. The concentration of EGF in each of 16 fully recovered 2-min perfusion samples was measured by RIA kit (Amersham, IL). The concentration of EGF in recovered NaCl perfusate varied between (mean +/- SEM) 1.78 +/- 0.19 and 2.14 +/- 0.14 ng/ml, whereas output varied between 9.25 +/- 0.98 and 11.14 +/- 0.82 ng/min. During perfusion with HCl, both the concentration of EGF within the esophageal perfusate and its secretion declined significantly to a value of 0.68 +/- 0.17 ng/ml (p < 0.0001) and 3.56 +/- 0.90 ng/min (p < 0.0001), respectively. Introduction of pepsin into an acidic perfusion solution (0.5 mg/ml of HCl) resulted in a significant increase in EGF concentration (1.99 +/- 0.36 ng/ml; p < 0.001) and output (10.24 +/- 1.84; p < 0.01), compared with EGF values recorded during perfusion with HCl. EGF output, calculated from a sealed 7.5-cm segment of the esophagus, was 10.39 +/- 0.89 ng/min, and was maintained at a steady state throughout an entire saline perfusion procedure. We present evidence that human esophageal mucosa has an enormous EGF secretory potential. The rapid esophageal EGF secretory response to intraluminal challenge with aggressive factors implies its role in the maintenance of the mucosal integrity.

Adult↗
PubMed1992

The effect of adhesive luting agent-dentinal surface interactions on film thickness.

This study investigated the effect of luting agent-dentinal surface interactions on the film thicknesses of new adhesive luting agents. The method was in compliance with American National Standards Institution/American Dental Association (ADA) Specification No. 8 for zinc phosphate cement. In the control groups the luting agents were placed between two glass plates, as described in ADA Specification No. 8, but in the test groups the luting agents were positioned between a glass and a dentinal plate. The materials selected were zinc phosphate cement, glass ionomer cement, polycarboxylate cement, and a resinous cement with a dentinal bonding agent. A two-way analysis of variance was performed, and t tests were computed to compare glass with the dentinal plate within each material. Zinc phosphate and glass ionomer cements exhibited a significant decrease in film thickness when measured in contact with dentin, as compared with contact with the glass plate. However, polycarboxylate cement and the resinous cement with its dentin bonding agent showed a slight nonsignificant increase when contacting dentin, as compared with the glass plate. An explanation was offered and suggestions were made regarding future research.

Adhesives↗
PubMed1992

Effect of seating force on film thickness of new adhesive luting agents.

This study examined the effect of seating force on the film thickness of new adhesive luting agents. The method was in compliance with American National Standards/American Dental Association Specification No. 8 for zinc phosphate cement. The materials tested were zinc phosphate cement, glass ionomer cement, polycarboxylate cement, and a resinous cement with a dentinal bonding agent. All materials were manipulated exactly as described in the manufacturer's instructions, and an electronic gauge with an accuracy of 0.5 micron was used. Each class of material was measured 10 times at six different seating forces. Analysis of variance and multiple comparisons testing disclosed that the seating force and class of material strongly influenced the film thicknesses of luting agents. A mathematical model describing the response of zinc phosphate cement within the range tested was reported.

Analysis of Variance↗
PubMed1992

Film thickness of new adhesive luting agents.

This study determined and compared the film thicknesses of new adhesive luting agents. The method was in compliance with American National Standards Institution/American Dental Association (ADA) Specification No. 8 for zinc phosphate cement. Each of the 20 materials tested was manipulated exactly as described in the manufacturers' instructions. An electronic gauge with an accuracy of 0.5 micron was recalibrated after each recording, and each luting agent was measured 10 times. The mean film thickness and standard deviation were calculated for each luting agent; an analysis of variance and a multiple comparison test were also performed. Nine materials satisfied the ADA type I specification for film thicknesses less than 25 microns, and these included a hydroxyapatite cement, glass ionomer cements, zinc phosphate cements, and polycarboxylate cements. Five other materials met the ADA type II specification for film thicknesses of less than 40 microns, and these included a glass ionomer cement, a resinous cement, a zinc phosphate cement, and glass ionomer-resinous hybrids. Six resinous cements recorded film thicknesses greater than 40 microns, and suggestions were made regarding future development and research.

Adhesives↗
PubMed1992

Nonconditional logistic regression analysis of risk factors in rheumatic heart disease.

The prognostic risk factors in 4323 patients with rheumatic heart disease, admitted from 1970 to 1990, were analysed. The overall mortality was 31.75% in this group of patients. Single factor analysis indicated that cardiac functional classification, time of death, month of death, cardiothoracic ratio, valvular lesions, cardiogenic shock, digitalis-induced arrhythmias, intercurrent pneumonia, pleurorrhea, and hypotension were related to the overall mortality and cardiac death. Multiple factor logistic analysis indicated that for the overall mortality, the independent prognostic factors included presence of cardiac functional classification, cardiothoracic ratio and cardiogenic shock; for cardiac death, the independent factors included cardiac functional classification, cardiothoracic ratio, cardiogenic shock, digitalis-induced arrhythmias and valvular lesions. The data analysis showed that these five factors were contributory to rheumatic heart disease with synergism.

Adolescent↗
PubMed1992

HPLC determination of a chemically modified nonantimicrobial tetracycline: biological implications.

Chemically modified tetracycline (4-de-dimethylamino tetracycline), like commercially available tetracyclines, is known to inhibit experimentally induced pathologic collagen breakdown. A method for measurement of chemically modified tetracycline in small volumes (50 microliters) of rat serum was developed using reversed-phase HPLC; this was necessary because this tetracycline analog lacks antimicrobial activity and, therefore, cannot be measured with standard bioassays. This method uses the same solution for extraction and elution thus providing a simple and rapid assay for both drugs. Using this technique, the concentration of chemically modified tetracycline and tetracycline were determined in rat serum at different times after oral administration. The serum concentration of chemically modified tetracycline was much higher than that for tetracycline, and its serum half-life was greater. The IC50 of chemically modified tetracycline and tetracycline, as inhibitors of collagenase from rat polymorphonuclear leukocytes, was determined and found to be 4.1 x 10(-8) M (0.02 micrograms/ml) and 2.4 x 10(-4) M (120 micrograms/ml), respectively. Based on the serum levels of these drugs after oral administration, and their IC50 values, chemically modified tetracycline is potentially a far more potent inhibitor of excess collagenase activity than tetracycline, during pathologic conditions, and may have the added advantage of not producing some of the typical complications of long-term antibiotic therapy.

Animals↗
PubMed1992

Genetic engineering of a Lymantria dispar nuclear polyhedrosis virus for expression of foreign genes.

A bacterial lacZ gene was inserted into an isolate of the Lymantria dispar nuclear polyhedrosis virus (LdMNPV). The transfer vector was constructed by site-directed mutagenesis of the translation start site of the LdMNPV polyhedrin gene, within the BglII E fragment of the viral genome. A multiple cloning sequence was inserted at this start site and used for the insertion of the lacZ gene into the transfer plasmid. Liposome transfection was used to cotransfect L. dispar tissue culture cells with viral DNA and the transfer plasmid. Recombinant LdMNPV isolates were purified by isolation of plaques producing beta-galactosidase but not polyhedra. Restriction enzyme fragment profiles were used to determine the site of the lacZ gene insertion, and DNA sequencing of the 5' and 3' ends of the lacZ gene insert and the adjoining polyhedrin promoter and coding regions was performed to identify its precise location. Expression of the lacZ gene was examined by studying virus-induced protein using [35S]methionine pulse-labelling, SDS-PAGE fractionation and autoradiography. Expression of beta-galactosidase was examined in tissue culture cells using colorimetric assays. The maximum rate of beta-galactosidase production was approximately 50 international units (IU)/10(6) tissue culture cells/day between 3 and 4 days post-infection (p.i), and the peak total expression was 158 IU/10(6) cells 5 days p.i. beta-Galactosidase activity was first detected 48 h p.i. in haemolymph samples from fourth instar L. dispar larvae injected with 10(6) p.f.u. of virus. The peak beta-galactosidase activity in larval haemolymph samples was 1931 IU/ml of haemolymph at 11 days p.i., just prior to death.

Animals↗