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PubMed1997

Combining heat treatment and subsequent incubation temperature to prevent growth from spores of non-proteolytic Clostridium botulinum.

Refrigerated processed foods of extended durability rely on a mild heat treatment combined with refrigerated storage to ensure microbiological safety and quality. The principal microbiological safety risk in foods of this type is non-proteolytic Clostridium botulinum. In this article the combined effect of mild heat treatment and refrigerated storage on the time to growth and probability of growth from spores of non-proteolytic Cl. botulinum is described. Spores of non-proteolytic Cl. botulinum (two strains each of type B, E and F) were heated at 90 degrees C for between 0 and 60 min and subsequently incubated at 5 degrees, 10 degrees or 30 degrees C in PYGS broth in the presence or absence of lysozyme. The number of spores that resulted in turbidity depended on the combination of heat treatment, incubation time and incubation temperature they received. Heating at 90 degrees C for 1 or more min ensured a 10(6) reduction when spores were subsequently incubated at 5 degrees C for up to 23 weeks. Heating at 90 degrees C for 60 min ensured a 10(6) reduction over 23 weeks when subsequent incubation was at 10 degrees C in the presence of added lysozyme. The same treatment did not reduce the spore population by 10(6) when subsequent incubation was at 30 degrees C.

Bacteriological Techniques↗

PubMed1992

Effect of puparia incubation temperature: increased infection rates of Trypanosoma congolense in Glossina morsitans centralis, G. fuscipes fuscipes and G. brevipalpis.

Puparia of Glossina morsitans centralis (Machado), G.fuscipes fuscipes (Newstead) and G.brevipalpis (Newstead) were incubated at 25 +/- 1 degrees C, 28 +/- 1:25 +/- 1 degrees C, day:night or 29 +/- 1 degrees C throughout the puparial period, and maintained at 70-80% relative humidity. Puparial mortality was higher at 29 than at 25 degrees C (optimum temperature) in all three species, particularly in G.f.fuscipes and G.brevipalpis. Adults of G.m.centralis from puparia incubated at 29 degrees C, and those of this subspecies, G.f.fuscipes and G.brevipalpis from puparia incubated at 28:25 degrees C, day:night or 25 degrees C throughout, were infected as tenerals (27 h old) by feeding them at the same time on goats infected with Trypanosoma congolense (Broden) IL 1180 after the parasites were detected in the wet blood film. Infection rates on day 25 post-infected feed were higher in G.m.centralis from puparia incubated at 29 degrees C and in adults of the three different tsetse species from puparia incubated at 28:25 degrees C, day:night, than in those from puparia incubated at 25 degrees C. However, in G.f.fuscipes the labral and hypopharyngeal infection rates were not significantly different from those of the tsetse produced by puparia kept at 25 degrees C.

Animals↗

PubMed1993

The effect of incubation temperature on the specificity of the BANA (N-benzoyl-DL-arginine-naphthylamide) test.

The hydrolysis of BANA by subgingival plaque samples is associated with the presence of either Treponema denticola, Porphyromonas gingivalis, and/or Bacteroides forsythus. A protocol in which pure cultures were incubated for 15 min at 55 degrees C detected about 5 x 10(5) CFU of P. gingivalis and 1 x 10(6) CFU of T. denticola. Clinical studies indicated that the BANA test in this configuration will detect about 10(4) organisms in vivo as compared with the 10(5) to 10(6) organisms found with in vitro grown cells. The BANA test can be made less sensitive by decreasing the time and/or temperature of incubation, which could improve the specificity of the test. In the present study we determined the incubation parameters that would give optimal specificity when the plaque samples were removed from sites of gingival health. Twenty-six approximal plaque samples were taken from each of 90 clinically healthy subjects and incubated with the BANA substrate on PerioScan cards (Oral-B Laboratories) for 5 and 15 min at 35 degrees, 45 degrees, and 55 degrees C. Subjects were randomly assigned to the various temperatures. Wooden toothpicks were inserted interproximally in all sites anterior to distal of the first molars and then each side of the toothpick was wiped onto the PerioScan card. The specificity of the BANA test relative to clinical health was 96% when the cards were incubated for 5 min at 35 degrees C, but decreased to 50-70% when the cards were incubated for 15 min at 35 degrees C or for 5 and 15 min at 45 degrees C and 55 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1979

The influence of ionic strength, albumin and incubation time on the sensitivity of the indirect Coombs' test.

The sensitivity of the indirect Coombs' test was investigated using saline, albumin, or low ionic strength (LIS) in the incubation phase and an incubation time varying from 5 to 120 min. Titration of 41 antibodies showed that LIS always resulted in a higher or almost the same mean scores as the other solutions after the same incubation time. The maximum mean score was always higher with LIS than with saline and was reached after a shorter period of incubation, only 20--40 min even with the weakest antibodies. With LIS, a longer incubation time than 40 min resulted in a sudden decrease in mean score. The maximum mean score using saline or albumin was reached after 40--60 min incubation. The same mean score was obtained after only 15--20 min, when LIS was used. Albumin gave only slightly higher mean scores than saline.

Antibodies↗

PubMed1977

Effects of enrichment media and incubation conditions on isolating salmonellae from ground-meat filtrate.

Forty-eight combinations of enrichment media, secondary enrichment, incubation times and temperatures, and atmospheres were examined for their efficacy in recovering different serovars of Salmonella that had been inoculated into ground-meat extract. Variations included three selective-enrichment media, two (37 and 43 degrees C) incubation temperatures, two (24 and 48 h) incubation times, two (aerobic and anaerobic) incubation atmospheres, and secondary enrichment to two of the selective-enrichment media. The ratio of Salmonella to other microorganisms was 10: greater than 1,000,000. One-hundred and twenty-four tests were conducted for each enrichment under each condition of incubation. None of the methods recovered Salmonella in more than 60% of the trials. Salmonella typhimurium was recovered most frequently of the serovars tested; S. abortusovis was recovered least frequently. There was considerable variation in the results obtained by the different methods, but there was a statistically significant advantage in the 43 degrees C incubation temperature. Secondary enrichment in tetrathionate broth showed a statistically significant advantage over secondary enrichment in selenite broth. Secondary enrichment into a different medium from the primary enrichment also was advantageous.

Culture Media↗

PubMed1971

Influence of temperature of incubation and type of growth medium on pigmentation in Serratia marcescens.

Maximal amounts of prodigiosin were synthesized in either minimal or complete medium after incubation of cultures at 27 C for 7 days. Biosynthesis of prodigiosin began earlier and the range of temperature for formation was greater in complete medium. No prodigiosin was formed in either medium when cultures were incubated at 38 C; however, after a shift to 27 C, pigmentation ensued, provided the period of incubation at 38 C was not longer than 36 hr for minimal medium or 48 hr for complete medium. Washed, nonpigmented cells grown in either medium at 38 C for 72 hr could synthesize prodigiosin when suspended in saline at 27 C when casein hydrolysate was added. These suspensions produced less prodigiosin at a slower rate than did cultures growing in casein hydrolysate at 27 C without prior incubation at 38 C. Optimal concentration of casein hydrolysate for pigment formation by suspensions was 0.4%; optimal temperature was 27 C. Anaerobic incubation, shift back to 38 C, killing cells by heating, or chloramphenicol (25 mug/ml) inhibited pigmentation. Suspensions of washed cells forming pigment reached pH 8.0 to 8.3 rapidly and maintained this pH throughout incubation for 7 days. Measurements of viable count and of protein, plus other data, indicated that cellular multiplication did not occur in suspensions of washed cells during pigment formation. By this procedure utilizing a shift down in temperature, biosynthesis of prodigiosin by washed cells could be separated from multiplication of bacteria.

Anti-Bacterial Agents↗

PubMed1982

Controlled evaluation of the effect of atmosphere of incubation on detection of bacteremia and fungemia in supplemented peptone broth.

To evaluate the role of atmosphere of incubation in the detection of clinically important bacteremia and fungemia in adults, we compared the yield of microorganisms from 10,541 paired 5-ml samples of blood incubated aerobically and anaerobically. The medium, supplemented peptone broth (SPB) with 0.03% sodium polyanetholesulfonate, and the ratio of blood to broth (1:10) were the same for all cultures. Only cultures with adequate blood samples (greater than or equal to 80% of stated volume) were compared statistically. More fungi (P less than 10(-7) ) grew in continuously vented bottles of SPB. Aerobic incubation also favored (P less than 0.01) isolation of Neisseria gonorrhoeae and Eubacterium; more than 80% of these bacterial organisms were detected only in vented bottles. Anaerobic incubation (plugged venting units) did not significantly favor the isolation of any genus of microorganisms, although an estimated 11% more Bacteroidaceae grew in the unvented bottle of SPB. By comparison of our data with published results for other media, we conclude that the need for both aerobic and anaerobic incubation of blood cultures is dependent upon the medium used and the microorganisms likely to be encountered. Vented incubation of blood cultured in SPB is crucial for detection of fungi and some bacteria. Routine use of an unvented bottle of SPB may not be worthwhile for patients in whom Bacteroidaceae cause bacteremia infrequently. However, when Bacteroidaceae are suspected as the cause of sepsis, use of an unvented bottle of SPB is prudent.

Bacteria↗

PubMed1991

Effects of incubation time and temperature on microbiologic sampling procedures for hemodialysis fluids.

To prevent pyrogenic reactions and bacteremia in hemodialysis patients, the Association for the Advancement of Medical Instrumentation and the Centers for Disease Control recommend culturing of hemodialysis fluids (water and dialysate) at least once a month. The recommendations for total microbial counts are (i) less than or equal to 200 CFU/ml in water used to prepare dialysate or reprocess hemodialyzers and (ii) less than or equal to 2,000 CFU/ml for the dialysate. In accordance with the Association for the Advancement of Medical Instrumentation recommendations all cultures should be incubated at 37 degrees C for 48 h on suitable culture media, such as Trypticase soy agar, standard methods agar, or one of several commercially available assay systems. There have been suggestions that lower temperatures and longer incubation might improve the recovery of bacteria from water and dialysate. In this study bacterial recovery from various dialysis fluids (water, bicarbonate dialysate, and bicarbonate concentrate) at 30 and 37 degrees C was compared. Duplicate sets of samples were membrane filtered (pore size, 0.45 microns); one set was incubated at 30 degrees C and the other was incubated at 37 degrees C for 72 h. The number of visible colonies was counted every 24 h by using a dissecting microscope. No significant difference was observed in specimens incubated at 37 degrees C for 48 h compared with those incubated at 30 degrees C for 72 h. Also, bacterial recovery was significantly better when samples of bicarbonate dialysate or bicarbonate concentrate were plated on Trypticase soy agar as opposed to standard methods agar.

Bacteria↗

PubMed2001

Three days of incubation may be sufficient for routine blood cultures with BacT/Alert FAN blood culture bottles.

BacT/Alert FAN blood culture bottles have been shown to enhance the recovery of bacteria and yeast from blood compared with standard BacT/Alert bottles. It is well established that standard BacT/Alert blood culture bottles require no more than 5 days of incubation for the detection of routine bacteria and yeast. It is less clear, however, whether FAN bottles also routinely require 5 days of incubation. To address this question, we recently reviewed the results of 17,887 blood culture sets collected in FAN blood culture bottles at Geisinger Medical Center. Of these cultures, 1,780 were positive for bacteria or yeast, yielding a total of 1,242 clinically significant isolates. The numbers of isolates recovered on days 1, 2, 3, 4, and 5 were as follows: (values in parentheses are percentages of total significant isolates): 877 (71%), 269 (22%), 65 (5%), 18 (1%) and, 13 (1%), respectively. In total, 97.5% of all clinically significant isolates were detected in the first 3 days of incubation. Of the 31 significant isolates detected on day 4 or 5 of incubation, 17 were detected in concurrent blood cultures within the first 3 days of incubation. Chart reviews were conducted for the 13 patients with the remaining 14 isolates detected on day 4 or 5 to determine whether therapy was changed due to this blood culture result. Therapy was changed for only 1 patient. These results suggest that it may not be necessary to routinely incubate FAN blood culture bottles for more than 3 days.

Aerobiosis↗

PubMed1976

Effects of selective media and atmosphere of incubation on the isolation of group A streptococci.

The effects of selective media and atmosphere of incubation on the isolation of group A beta-hemolytic streptococci were evaluated. Sheep blood agar medium with gentamicin (2.5 or 5.0 mug/ml) was inferior to antibiotic-free sheep blood agar medium. This resulted from the partial restriction of group A streptococcal growth on gentamicin medium. Recovery of beta-hemolytic streptococci from specimens in air, CO2, or anaerobic incubation was evaluated. The isolation of group A streptococci was equivalent in the three incubation atmospheres; however, non-group A beta- hemolytic streptococci were isolated significantly more often from specimens incubated in an anaerobic or CO2 atmosphere than from those incubated in air. Therefore, sheep blood agar medium, stabbed with a wire loop and incubated in air, is recommended for the isolation of group A streptococci from throat swabs.

Agar↗

PubMed1991

The R-U5-5' leader sequence of neurovirulent wild mouse retrovirus contains an element controlling the incubation period of neurodegenerative disease.

The wild mouse ecotropic retrovirus CasBrE causes a spongiform neurodegenerative disease after neonatal inoculation, with an incubation period ranging from 2 to 12 months. We previously showed that introduction of long terminal repeat (LTR) and gag-pol sequences from a strain of Friend murine leukemia virus (FB29) resulted in a dramatic acceleration of the onset of the disease. The chimeric virus FrCasE, which consisted of the FB29 genome containing 3' pol and env sequences from the wild mouse virus, induced a highly predictable, lethal neurodegenerative disease with an incubation period of only 16 days. Here we report that the sequences which are primary determinants of the length of the incubation period are located in the 5' end of the viral genome between a KpnI site in the R region of the LTR and a PstI site immediately 5' of the start codon for pr65gag (R-U5-5' leader). This region contains the tRNA primer binding site, splice donor site for the subgenomic env mRNA, and the packaging sequence. Computer-assisted sequence analysis failed to find evidence of a consensus sequence for a DNA enhancer in this region. In addition, sequences within a region of the genome between a ClaI site at the 3' end of env to the KpnI site in the R region of the LTR (inclusive of U3) also influenced the incubation period of the disease, but the effect was distinctly weaker than that of the R-U5-5' leader sequence. This U3 effect, however, appeared to be independent of the number of direct repeats, since deletion of one of two duplicated 42-base repeats containing consensus sequences of nuclear-factor binding domains had no effect on the incubation period of the disease. On the basis of Southern blot analysis of total viral DNA in the tissues, the effect of these sequences on the incubation period appeared to be related to the level of virus replication in the central nervous system. All of the chimeric viruses analyzed, irrespective of neurovirulence, replicated to comparable levels in the spleen and induced comparable levels of viremia.

Amino Acid Sequence↗

PubMed1982

Effects of anaerobic and microaerophilic conditions of extraction and incubation on the survival of Treponema pallidum in vitro.

Treponema pallidum extracted from infected rabbit testes under anaerobic conditions survived longer in vitro than those extracted under aerobic conditions. Anaerobically extracted treponemes were incubated anaerobically for 0, 12, 24, 36, or 48 hours and then exposed to microaerophilic conditions (3% oxygen) for further incubation. Treponemes transferred to microaerophilic conditions after 36 or 48 hours' anaerobic incubation maintained significantly greater viability compared with those kept under constant microaerophilic conditions, although there was no difference after 12 or 24 hours. T pallidum incubated under constant anaerobic conditions, however, usually maintained greater viability than those kept under constant microaerophilic conditions. These results suggest that T pallidum is sensitive to oxygen toxicity both during initial extraction from orchitic rabbit testes and subsequent incubation in vitro. In the latter case, it can be partially protected by a period of anaerobic incubation in vitro, before exposure to microaerophilic conditions.

Anaerobiosis↗

PubMed2006

Viability of the isolated soleus muscle during long-term incubation.

Skeletal muscle metabolism has been examined in perfused hindlimb muscles and in isolated muscle preparations. While long-term viability of the fast-twitch epitrochlearis has been documented with respect to glucose transport, it appears that long-term incubated soleus muscles are less stable when incubated ex vivo for many hours. Therefore, in the present study, we have examined whether the isolated soleus muscle remains metabolically viable for up to 18 h with respect to maintaining ATP and phosphocreatine (PCr) concentrations, carbohydrate and fatty-acid metabolism, insulin signalling, and protein expression. Soleus muscles were incubated in well-oxygenated Medium 199 (M199) supplemented with low concentrations of insulin (14.3 microU/mL) for 0, 6, 12, and 18 h. During this incubating period the concentrations of ATP and PCr were stable, indicating that oxygenation and substrate supply were being maintained. In addition, the concentrations of proglycogen and macroglycogen were not altered, whereas an increase (+30%) in intramuscular triacylglycerol concentration was observed at the end of 18 h of incubation (p < 0.05). Complex molecular processes in the long-term incubated muscles were also stable. This was shown by maintenance of basal as well as insulin-stimulated rates of 3-O-methyl glucose transport, and by the maintenance of protein expression of the glucose transporter GLUT4 and the fatty acid transporters FAT/CD36 and FABPpm. In addition, the insulin-stimulated translocation of GLUT4 to the plasma membrane, which involves a complex signalling cascade, was fully preserved. In conclusion, in well-oxygenated soleus muscles maintained in M199 supplemented with extremely low concentrations of insulin, ATP and PCr concentrations, carbohydrate and fatty acid metabolism, insulin signalling, and protein expression were stably maintained for up to 18 h. This provides for opportunities to examine muscle metabolic function under very highly controlled conditions.

3-O-Methylglucose↗

PubMed1975

An incubation medium for the elevation of adenosine triphosphate and 2,3-diphosphoglycerate in fresh and long-preserved human erythrocytes.

The levels of adenosine triphosphate (ATP) and 2,3-diphosphoglycerate in freshly drawn human erythrocytes can be tripled by a 2 h incubation at 37 degrees C in a medium containing 21 mM glucose, 1.8 mM adenine, 5 mM pyruvate, 10 mM inosine, and 96 mM phosphate. Similar incubation conditions will restore the levels of ATP and 2,3-diphosphoglycerate in erythrocytes from blood levels preserved for 12 and 15 weeks, respectively, to those of fresh cells. Omission of pyruvate from the incubation medium further increases the level of ATP slightly, but there is little elevation of 2,3-diphosphoglycerate. Under these conditions labelled pyruvate and lactate production from [14-C]glucose or [14-C]inosine is not diminished, but labelled fructose 1,6-diphosphate, rather than 2,3-diphosphoglycerate, accumulates. In addition, omission of pyruvate from the incubation medium, with a concomitant decrease in accumulation of 2,3-diphosphoglycerate, diminishes the concentration of inorganic phosphate required for optimal ATP elevation. A 5 h incubation in the glucose-adenine-pyruvate-inosine-phosphate medium elevates the levels of ATP and 2,3-diphosphoglycerate in erythrocytes from blood preserved in the cold for 15 weeks to twice that of fresh cells, indicating that the cells retain their metabolic potential even after prolonged storage at 2 degrees C. The medium may provide a method of rejuvenating 10-12 week cold-preserved erythrocytes for transfusion purposes, by a 1 h incubation at 37 degrees C.

Adenine↗

PubMed1990

Fatty acid release in incubations of serum with synaptosome and myelin subfractions of brain.

To study lipid breakdown in brain membranes following hemorrhage, synaptosome and myelin fractions isolated from rat brain were incubated with rat serum. After 3 h in vitro at 37 degrees C, 0.43 and 0.26 mumol of fatty acid were released in incubations containing synaptosomes (1.37 mumols phospholipid) or myelin (1.23 mumols phospholipid), respectively, in the presence of 0.25 mL serum. Less than 0.05 mumol of fatty acid was liberated in incubations containing only serum, synaptosomes, or myelin. For synaptosomes and serum, docosahexaenoate was the principal fatty acid released (28 mol% of total) after 3 h of incubation. This fatty acid and arachidonate made up 43 mol% of the liberated fatty acid. The presence of free docosahexaenoate was of interest, as this fatty acid is particularly enriched in phosphatidylserine and phosphatidylethanolamine, phospholipids found in the cytoplasmic half of the synaptosomal plasma membrane and in interior synaptosomal membranes. In incubations of serum and myelin, oleate was the major free fatty acid produced in 30 min to 3 h of incubation (29-35 mol% of total). After 3 h, docosahexaenoate contributed 20 mol% to the total. The release of fatty acids from the membranes may be mediated by serum phospholipase(s) or possibly by activated endogenous lipolytic activities.

Animals↗

PubMed1991

Prolonged incubation of skeletal muscle increases system A amino acid transport.

During the course of experiments involving prolonged incubation of skeletal muscle, we observed large increases in system A amino acid transport activity. System A activity was monitored with the nonmetabolizable amino acid analogue alpha-(methylamino)isobutyrate (MeAIB). When rat epitrochlearis muscles are incubated in Krebs-Henseleit buffer supplemented with 0.1% bovine serum albumin and 8 mM glucose, basal MeAIB transport doubles after 5 h and is elevated approximately sevenfold after 9 h compared with rates measured in muscles incubated for 1 h. Insulin-stimulated transport also doubles after 5 h and increases by fourfold after 9 h. The increases in basal and insulin-stimulated system A transport over time can be prevented by incubating muscles in the presence of cycloheximide. Addition of minimum essential medium essential amino acids (EAA) to the incubation medium blocks the increase in basal and insulin-stimulated MeAIB transport measured after 9 h by 85-90 and 60%, respectively. A single amino acid, glutamine, can account for half of the inhibitory effect of EAA on the time-dependent increase in basal system A transport. Amino acid metabolism is not necessary for inhibition of the rise in basal MeAIB transport. At concentrations normally present in minimum essential medium, nonessential amino acids are less effective (51% inhibition) in preventing the rise in basal transport occurring over 9 h. At three times normal concentrations, however, the ability of nonessential amino acids to prevent the time-dependent increases in basal and insulin-stimulated MeAIB transport is comparable to that of EAA. These changes in MeAIB transport with prolonged incubation are not due to muscle deterioration.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗

PubMed2006

Electrolysis stimulates creatine transport and transporter cell surface expression in incubated mouse skeletal muscle: potential role of ROS.

Electrical field stimulation of isolated, incubated rodent skeletal muscles is a frequently used model to study the effects of contractions on muscle metabolism. In this study, this model was used to investigate the effects of electrically stimulated contractions on creatine transport. Soleus and extensor digitorum longus muscles of male NMRI mice (35-50 g) were incubated in an oxygenated Krebs buffer between platinum electrodes. Muscles were exposed to [(14)C]creatine for 30 min after either 12 min of repeated tetanic isometric contractions (contractions) or electrical stimulation of only the buffer before incubation of the muscle (electrolysis). Electrolysis was also investigated in the presence of the reactive oxygen species (ROS) scavenging enzymes superoxide dismutase (SOD) and catalase. Both contractions and (to a lesser degree) electrolysis stimulated creatine transport severalfold over basal. The amount of electrolysis, but not contractile activity, induced (determined) creatine transport stimulation. Incubation with SOD and catalase at 100 and 200 U/ml decreased electrolysis-induced creatine transport by approximately 50 and approximately 100%, respectively. The electrolysis effects on creatine uptake were completely inhibited by beta-guanidino propionic acid, a competitive inhibitor of (creatine for) the creatine transporter (CRT), and were accompanied by increased cell surface expression of CRT. Muscle glucose transport was not affected by electrolysis. The present results indicate that electrical field stimulation of incubated mouse muscles, independently of contractions per se, stimulates creatine transport by a mechanism that depends on electrolysis-induced formation of ROS in the incubation buffer. The increased creatine uptake is paralleled by an increased cell surface expression of the creatine transporter.

Animals↗

PubMed1996

Regulation of chicken gonadotropin-releasing hormone-I mRNA in incubating, nest-deprived and laying bantam hens.

Secretion of luteinizing hormone is decreased when hens start to incubate their eggs and is increased after nest deprivation or hatching of the eggs. The purpose of this study was to determine whether decreased luteinizing hormone (LH) secretion during incubation in the domestic hen is associated with a decrease in hypothalamic chicken gonadotropin-releasing hormone-I (cGnRH-I) mRNA or peptide. A semiquantitative competitive PCR assay was developed to measure cGnRH-I mRNA. Hypothalamic mRNA was quantified as the amount of GnRH cDNA obtained by reverse transcription of cGnRH-I mRNA. The amount of hypothalamic cGnRH-I mRNA was significantly higher in laying than in incubating hens (38.7 +/- 10.3 vs. 7.7 +/- 1.6 x 10(-17) mol cDNA, p = 0.01, n = 8). The hypothalamic GnRH peptide content was not significantly different between laying and incubating hens in either the preoptic area (286.9 +/- 24.01 vs. 269.3 +/- 29.3 pg, n = 8) or the basal hypothalamus (1.67 +/- 0.19 vs. 1.54 +/- 0.21 ng, n = 8). Five days after incubating hens were deprived of their eggs, the resulting increase in LH secretion was associated with a significant increase in hypothalamic content of cGnRH-I mRNA (22.8 +/- 2.2 vs. 6.7 +/- 1.7 x 10(-17) mol cDNA, p < 0.001, n = 8). These observations suggest that a decrease in the expression of the cGnRH-I gene is a major factor in maintaining depressed LH secretion in incubating domestic chickens.

Animals↗