Prostaglandin fever in rats is altered by kainic acid lesions of the ventral septal area

The ventral septal area (VSA) has been shown to be a region within the rat brain where arginine vasopressin (AVP) acts to reduce fever. To test the hypothesis that destruction of this area would affect the magnitude of the febrile response, body temperature was monitored in male, Wistar rats given intracerebroventricular injections of prostaglandin E1 (200 ng) and saline (10 microliter) before and after bilateral injections of kainic acid (KA) or of saline vehicle into the VSA. While fever heights were unaffected by the lesion, fever in the KA-lesioned animals remained significantly elevated (P less than 0.05) for 1 h after the peak response. There was no significant difference in the fever responses displayed by sham-lesioned animals. The body temperature response of non-febrile animals to high or low ambient temperature was unaffected by the lesions. The enhanced fever following the KA lesion, but not sham lesions of the VSA would support the hypothesis that this region is involved in endogenous suppression of fever.

The role of vasopressin as an antipyretic in the ventral septal area and its possible involvement in convulsive disorders

Perfusion of the peptide, arginine vasopressin (AVP), within the ventral septal area (VSA) of the brain of a number of species reduces fever but not normal body temperature. This antipyretic response appears to be mediated by AVP receptors of the V1 subtype. Lesions of the VSA with kainic acid are associated with prolonged and enhanced fevers in rats. A role for endogenous AVP in fever suppression within the VSA comes from several types of experiments: (1) AVP release within the VSA is inversely correlated to fever height; (2) AVP antagonists or antiserum injected into the VSA prolong fever; (3) animals lacking endogenous AVP in the VSA (Brattleboro rat, long-term castrated rat) develop enhanced fevers. Electrical stimulation of the AVP-containing cell bodies of the bed nucleus of the stria terminalis (BST) orthodromically inhibits VSA neurons and also suppresses fever; the latter effect can be abolished with application of a V1 antagonist to the VSA. Iontophoretic studies indicate that AVP inhibits glutamate-stimulated activity of thermoresponsive and other VSA neurons. AVP can also act in the VSA to cause severe motor disturbances; this action is receptor mediated and increases in severity upon sequential exposure to AVP. Because sites of action of the antipyretic and convulsive action of AVP are similar, and because animals lacking brain AVP display reduced convulsive activity, it is possible that AVP, released during fever, could be involved in the genesis of convulsive activity.

Recommendations for the use of Taylor series confidence intervals for estimates of vaccine efficacy

A simple formula for calculating confidence intervals by means of a Taylor series variance approximation has been recommended for gauging the precision of estimates of vaccine efficacy. To evaluate the performance of Taylor series 95% confidence intervals for vaccine efficacy, we conducted a simulation study for commonly expected values of vaccine efficacy, risk of disease in the unvaccinated population, and sample sizes of the vaccinated and unvaccinated groups. In the first simulation, the sample size in the vaccinated group was 500 or 1000, whereas that in the unvaccinated group ranged from 10 to 1000. The confidence intervals were accurate when the sample size in the unvaccinated group was >/=50 and the risk of disease was 0.3-0.9. In contrast, the intervals were too narrow when all three of the following situations occurred: the number of unvaccinated was small (10 or 20), the true vaccine efficacy was relatively low (60% or 80%), and the risk of disease was 0.5-0.9. Furthermore, when the true vaccine efficacy was high (90% or 95%) and the disease risk in the unvaccinated was low (0.1 and 0.2), the confidence intervals were too broad, especially when the unvaccinated sample size was <50. Additional simulations with a sample size in the vaccinated group of 200 gave broad intervals for 95% vaccine efficacy (for all values of disease risk) and for 90% vaccine efficacy when the disease risk was </=0.3.

Yersinia enterocolitica infections and pork: the missing link

To determine the risk factors for Yersinia enterocolitica (YE) infection in Belgium, which is the country with the highest incidence of this infection, 40 persons with YE infections due to serotype O:3 (n = 36) or O:9 (n = 4) were compared with matched controls. Most patients had acute gastroenteritis; 1 had a liver abscess. 20% were admitted to hospital; the mean duration of hospital stay was 9 days. YE infection was strongly associated with eating raw pork in the 2 weeks before onset (odds ratio = 12, p = 0.00002), a factor that accounted for 58% of the YE infections studied. 14 (18%) of 79 families surveyed at a well-baby clinic fed their children raw pork from a median age of 18 months. Specific control measures to reduce contamination and consumption of raw pork may reduce the incidence of YE infections.

Mathematical separation of multi-component exponential signals from the u.v. laser excitation of glycogen phosphorylase b

Laser excitation of the vitamin B6 cofactor of the glycogen phosphorylase enzyme produces a transient absorbance signal at 470 nm. Martin et al. proposed four exponential decays for this complex signal. One component with the largest amplitude and a decay rate constant in the region of 150,000 s-1 results from an excited singlet state, and three successive decays of smaller amplitude with the rate constants in the regions of 700,000 s-1, 30,000 s-1, and 6000 s-1 result from a triplet state. These results were determined through nonlinear least squares regression and residual analyses, with some knowledge of the possible photochemistry of the cofactor by itself. The Fourier transform method, which requires no initial estimates of the parameters or of the number of decays, was selected for further analysis of the data. The results of the Gardner and differential approaches to the method confirm that the predicted four exponential components are in the signal and that the values of the decay rate constants agree with those from the nonlinear regression analysis. These results, presented here, help to demonstrate protein changes at the active site of enzyme catalysis.

Protein dynamics of glycogen phosphorylase

The glycogen phosphorylase molecule absorbs the ultraviolet energy of a nitrogen laser to form an excited state of the cofactor. The decay rate of this state has a lifetime of 6.7 microseconds, and its sensitivity to bound substrates presents a new perspective of the mechanism. A careful analysis of the decay curve for native enzyme and cofactor analogues showed that the lifetime depends on the conformation of protein groups at the active site and how the residues change with bound substrate. The reactive ternary complexes obtained from either direction of the reaction yielded the same lifetime, indicating a change in the active-site conformation to a common configuration for the cofactor and substrate phosphate. This configuration indicates an increase in the cofactor 5'-PO4 pKa and a possible proton shuttle. The pyridoxal 5'-pyrophosphate reconstituted enzyme showed no conformational change alone or in the presence of oligosaccharide. This result does not support an electrophilic attack by the 5'-PO4 phosphorus.

The action of centrally administered arginine vasopressin on blood pressure in the conscious rabbit

In addition to its peripheral endocrine actions, arginine vasopressin (AVP) has been implicated in the central control of blood pressure. Intracerebroventricular (i.c.v.) injections (0.01-1.0 nmol) of AVP or arginine vasotocin (AVT), but not oxytocin (OXY), into unanesthetized rabbits caused a rapid, dose related rise in blood pressure as well as increases in heart rate. The lowest centrally administered dose of AVP and AVT (0.01 nmol) had no effect on blood pressure when given intravenously. In search of tissue locus for the pressor effect of AVP microinjection of AVP and OXY into the posterior hypothalamus and septum of conscious rabbits was without effect. However, microinjection (0.01-0.04 nmol) of AVP into the nucleus tractus solitarius of anesthetized rabbits caused a rise in blood pressure similar to the response seen after i.c.v. injection. Comparable volumes of the vehicle into the ventricle or the tissue sites had no effect on resting blood pressure. The pressor response after AVP given i.c.v. was significantly reduced up to 3 h after administration of the ganglionic blocker, chlorisondamine HCl. The central antagonist, d(CH2)5Tyr (Me) vasopressin, eliminated the usual increase in blood pressure after administration of AVP in half the animals tested. The results indicate that AVP acts centrally to mediate cardiovascular responses in unanesthetized as well as anesthetized rabbits.

Propagation of Rhizopus javanicus Biosorbent

After propagation of Rhizopus javanicus in defined media containing glucose, urea, and mineral salts in deionized distilled water, the ability of the nonliving biomass to sequester cupric ion was assayed. Growth, uptake capacity (saturation uptake at >1 mM Cu 2+ concentration in solution), and biosorptive yield (biomass concentration × uptake capacity) were increased by augmentation of the growth medium with mineral salts once growth was under way. In the stationary phase, the uptake capacity of mycelia, which were normally a poor biosorbent, was improved within 4 h of trace metal addition to the growth medium. Growth of the culture was inhibited by excessive concentrations (0.04 to 40 μM) of metals in the medium in the following order: Cu > Co ≥ Ni > Mn > Mo; zinc was not inhibitory at 40 μM, and chromium was stimulatory at 0.53 μM but slightly inhibitory at higher levels. Iron and potassium phosphate stimulated growth at levels of 0.53 and 40 mM, respectively. When R. javanicus was propagated in a medium with a high salt concentration, exponential growth (0.23 h −1 ) to a biomass concentration of >3 g/liter and a biosorptive yield of >500 μmol/liter was achieved. It is evident that the powerful biosorbent characteristics of Rhizopus biomass led to depletion of available trace minerals in suspension culture, which in turn limited growth.

Importance of host factors in human salmonellosis caused by multiresistant strains of Salmonella

Antimicrobial resistance patterns of Salmonella isolates from persons in randomly selected urban and rural counties in the United States were examined along with clinical and epidemiological characteristics of the host. Multiresistant strains, isolated from 66 (12.2%) of 542 persons evaluated, were associated with five of 20 variables in univariate analyses: serotype heidelberg, host of Hispanic origin, host exposure to penicillins within four weeks before stool culture, age greater than or equal to 60 years, and regular antacid use. By multiple linear regression, the first three variables were each significantly associated with infections due to multiresistant Salmonella. One or more of the last three variables, thought to be host factors that may promote disease, were present for persons yielding 38% of multiresistant strains but only 12% of sensitive strains (P less than .001). The relatively large proportion of multiresistant Salmonella among isolates from persons with these risk factors suggests that to cause disease, resistant organisms are more dependent than are sensitive organisms on host characteristics.

A technique for determining prosthetic joint contact areas

A technique to determine the contact areas of total joint replacements has been developed. A thin film of petroleum jelly is deposited by the metallic component on the plastic component when load is applied. Fingerprint powder is then used to highlight the petroleum jelly coated area. Experimental data produced using this technique was found to be in good agreement with theoretical predictions.

Effects of cortisol administration on development of the thyroid and adrenal axes in rats

Intraperitoneal (IP) injections of cortisol were administered to neonatal male rats on postnatal days 1 to 4. Plasma triiodothyronine (T3), thyroxine (T4) and corticosteroids were determined on days 5, 10, 13, 16, 20, 30 and 60 of age, and all animals were weighed weekly. Neonatal cortisol treatment resulted in depressed body weight gain and transient depression in plasma T4. These results indicate that while body weight is significantly affected by cortisol treatment ontogenic patterns of plasma T3, T4 and corticosteroids develop normally.

Intravenous nitroglycerin in acute coronary artery disease

Intravenous nitroglycerin (IVNG) was used in 12 instances (11 patients) to relieve pain, following myocardial infarction or unstable angina. The strength of IVNG infusion could be easily controlled and relief of pain was prompt and satisfactory. Excessive tachycardia or severe headache was not encountered and marked hypotension was seen in one patient only. This patient had three vessel coronary artery disease, extensive myocardial damage and vein graft closure. Cardiovascular stability was provided by IVNG, prior to and during cardiac catheterisation and cineangiography, transportation to another hospital and vein graft surgery. IVNG appears to be a safe and effective drug in the management of patients with acute coronary artery disease (unstable angina and myocardial infarction). In those with both right and left ventricular wall infarction, however, the usefulness of IVNG needs to be established.

Secular trends in nosocomial infections: 1970-1979

Nosocomial infection data from a mean of 81 hospitals has been reported to the National Nosocomial Infections Study (NNIS) each year since 1970. Surveillance has been conducted by the hospitals on an average of 1.16 million patients annually. The median nosocomial infection rate is 341 per 10,000 patients discharged, ranging from 312 in 1970 to 358 in 1975. Since 1975, the rate has steadily declined to 329 in 1979. By category of hospital, infection rates for community-teaching and municipal hospitals have declined in recent years whereas those for community and university hospitals have not. Infection rates for patients on the surgical service have declined steadily since 1975 to the lowest levels reported, 457 per 10,000 surgical patients discharged in 1979, primarily due to a decrease in the rate of surgical wound infections. On obstetrics, infection rates have increased steadily since 1970, also primarily due to surgical wound infections. Bacteremias have increased in frequency, particularly those associated with infection at other sites. No major shifts have been noted in the relative frequency of the most common sites of infection or pathogens causing infections.

Factors affecting the production of hydrogenase by Desulfovibrio desulfuricans

An examination of conditions for the growth of Desulfovibrio desulfuricans, with the aim of optimizing hydrogenase production, is reported. An ammonium sulfate-lactate-yeast extract medium gave 5 to 10 times as much hydrogenase activity as a peptone-yeast extract medium. It made little if any difference whether the gas used for sparging was nitrogen, hydrogen, or a mixture thereof but increasing the rate of sparging and agitation did result in a slight decrease in activity. Control of pH during culture development was of little benefit to hydrogenase production. At least two hydrogenases were present in D. desulfuricans: one periplasmic, the other membrane bound.

Purification and properties of the periplasmic hydrogenase from Desulfovibrio desulfuricans

The periplasmic hydrogenase of Desulfovibrio desulfuricans was isolated and purified. Cells were washed with Tris-EDTA and the enzyme precipitated from the wash with ammonium sulfate. Absorption chromatography on DEAE and hydroxyapatite yielded the enzyme at better than 95% purity as judged by gel electrophoresis. The hydrogenase catalyzed the production of more than 9000 mumol H2/min mg protein(-1) from reduced methyl viologen at 37 degrees C. It is very stable and resists inactivation by heat (50% activity remained after 5 min in air at 65 degrees C) and by enzyme inhibitors (except N-ethylmaleimide and potassium ferricyanide). After storage in air at 4 degrees C for 1 month no activity was lost. The enzyme activity is sensitive to ionic environmental changes. With methyl viologen the optimum pH was 5.5 but with p-xylene polymeric viologen the optimum was about pH 7 but less sharp. The molecular weight was 47 X 10(3)(+/- 2 X 10(3), 52 X 10(3)(+/- X 10(3), and 56 X 19(3)(+/- 2 X 10(3) by SDS-gel electrophoresis, gel chromatography, and sedimentation equilibrium, respectively, and the isoelectric point was at pH 6.0. They enzyme might be useful in the production of hydrogen from water and solar energy.

DNA-mediated transformation in mutants of phage group 2 Staphylococcus aureus

A large pool of antibiotic resistant and auxotrophic mutants was isolated from the Staphylococcus aureus phage group 2 strains UT0002-19 and UT0017 by (1) antibiotic gradient plates, (2) trimethoprim selection, and (3) nitrosoguanidine mutagenesis, which sometimes was coupled by enrichment with either penicillin or methicillin. Strain UT0002-19 has a chromosomal determinant for exfoliative toxin (ET), which causes "scalded skin syndrome" in man. A few mutants were isolated from the phage group 1 strain UT0080, which also produces ET. Two transformation regimens, called the broth and plate methods, were devised for the phage group 2 strains. They employed 80 alpha as helper phage, and recipient cells were incubated with transforming DNA in the presence of Ca2+. Strain UT0080 was transformed using phage 55 as helper. Maximum competence of the phage group 2 strains occurred during early logarithmic growth in trypticase soy broth, but cells grown overnight on heart infusion agar were also competent. Transformation frequencies of all markers ranged from 10(-6) to 10(-8). For phage 80 alpha, a multiplicity of infection of 4 was optimal in transforming a mutant of strain UT0002-19. Transformation of gly, lin, met, ole, rif, and ser markers in S. aureus is reported for the first time. Ery and ole markers in all three strains exhibited cross-resistance. Mapping studies, similar to those performed by DNA-mediated transformation in the phage group 3 strain 8325, can now be commenced for phage group 2 strains of S. aureus in order to elucidate the molecular genetics of this medically important bacterium.

Rapid growth of Acanthamoeba in defined media; induction of encystment by glucose-acetate starvation

Defined media are described that support 14-20 h generation times for Acanthamoeba castellanii and A. rhysodes in monolayer cultures. The media differ in minor ways from previously described media, but the growth rates are greatly improved over previously reported values. Maximum growth rates were observed for A. castellanii in a complex medium containing 21 amino acids, but near-maximum rates could be achieved in relatively simple media containing 9 amino acids. Growth occurred with 6 amino acids, as reported by others, but generation times exceeded 30 h. Amitosis was a common problem during early subcultures in defined media, defined media by glucose and acetate starvation. The rate of encystment varied with cell density at the time of starvation and was optimal at initial densities of 400-800 amebae/mm2.

Severe illness with influenza B

Fifteen patients with recent influenza B infection were admitted to three Dallas hospitals in the first 11 weeks of 1977. The patients' ages ranged from five to 73 years, with a median of 18 years. Most had no significant underlying disease. The spectrum of clinical illness included postinfluenzal bacterial pneumonia (three cases), other severe chest disease (two cases), hyperpyrexia and possible rhabdomyolysis in the elderly (two cases), onset of toxemia of pregnancy, thyroid dysfunction, Stevens-Johnson syndrome, neurologic disorders (two cases), and Reye's syndrome (three cases). Two patients died. Two elderly men with high fever and weakness entered the hospital within three days of illness and two of three patients with Reye's syndrome were admitted four days after the onset of influenza, but the 11 other patients gave a history of seven to 31 days of symptoms before being hospitalized. Morbidity and mortality with influenza B are neither trivial nor restricted to debilitated hosts.

Genetic mapping in phage group 2 Staphylococcus aureus

Two regimens for transformation have been devised for the phage group 2 strains UT0002-19 and UT0017 of Staphylococcus aureus. Strain UT0002-19 produces exfoliative toxin, which is responsible for the clinical manifestations of the staphylococcal scalded skin syndrome, whereas strain UT0017 does not produce exfoliative toxin. A large pool of antibiotic-resistant and auxotrophic mutants from strains UT0002-19 and UT0017 were isolated by using (i) antibiotic gradient plates, (ii) trimethoprim selection, and (iii) nitrosoguanidine mutagenesis, which sometimes was coupled by enrichment with penicillin or methicillin. Transformation frequencies of genetic markers in mutant strains ranged from 10(-6) to 10(-8). Three genetic linkage groups were identified on the strain UT0017 chromosome. The first linkage group was thy-4-lys-5-trp-21-thr-4, the second was pyr-26-nov-9-his-3, and the third consisted of ilv-9 and pen-1, a genetic determinant for beta-lactamase synthesis. Two linkage groups were detected on the strain UT0002-19 CHROMOSOMe. The first was defined as thy-1-lys-5-trp-3-thr-4-ala-8, whereas the second consisted of nov-9 and his-3 markers. A chromosomal locus that controlled synthesis of exfoliative toxin could not be mapped.

Legionnaires' disease: clinical features of the epidemic in Philadelphia

A review of the medical records of 123 persons with Legionnaires' disease hospitalized in the 1976 Philadelphia epidemic showed that the manifestations of infection ranged from mild grippe to a severe pneumonia that also involved other organ systems. Early in the illness, constitutional symptoms predominated. Fever, malaise, myalgia, rigors, confusion, headache, and diarrhea were usually followed by nonproductive cough and dyspnea. Physical examination showed few abnormalities other than rales. Moderate leukocytosis with left shift, elevated erythrocyte sedimentation rate, elevation of serum levels of liver enzymes, and hematuria and proteinuria were characteristic. Chest radiograph showed patchy, often nodular, areas of consolidation. Progression of pneumonia led to respiratory failure and the need for mechanical ventilatory assistance for 19 patients; renal failure, primarily after shock, occurred in 18 persons. Twenty-six patients died. Treatment with erythromycin or tetracycline resulted in the lowest case-fatality ratios, but the associations were not statistically significant.

The role of nationwide nosocomial infection surveillance in detecting epidemic bacteremia due to contaminated intravenous fluids

Since January, 1970, the Center for Disease Control (CDC) has corridnated surveillance of nosocomial infections in a group of voluntarily cooperating hispitals in the United States. In 1970, this surveillance system failed to realize one of its major goals: detection of a nationwide epidemic of septicemia caused by contaminated intravenous products. However, retrospective review of infections reported to CDC revealed that the data received were sufficient for the outbreak to have been recognized. Beginning in July, 1970, one month after the contaminated products were first distributed and five months before the outbreak was actually detected. CDC data showed a persistent increase in the incidence of Enterobacter and Erwinia (presently designated Enterobacter agglomerans) bacteremia. Furthermore, monthly rates of cases of bacteremia caused by these organisms were higher in hospitals using the contaminated intravenous products than for hospitals not using them. Failure to detect this outbreak at the time of its occurrence was due to delays in data processing and insufficiently sophisticated data analysis. Based on this experience, CDC has modified the surveillance system to aid recognition of future outbreaks.

Legionnaires' disease: description of an epidemic of pneumonia

An explosive, common-source outbreak of pneumonia caused by a previously unrecognized bacterium affected primarily persons attending an American Legion convention in Philadelphia in July, 1976. Twenty-nine of 182 cases were fatal. Spread of the bacterium appeared to be air borne. The source of the bacterium was not found, but epidemiologic analysis suggested that exposure may have occurred in the lobby of the headquarters hotel or in the area immediately surrounding the hotel. Person-to-person spread seemed not to have occurred. Many hotel employees appeared to be immune, suggesting that the agent may have been present in the vicinity, perhaps intermittently, for two or more years.

Growth of plant cell suspension cultures with ammonium as the sole source of nitrogen

Most media for the culture of plant cells contain two or more sources of nitrogen, and these appear to serve in part to balance changes in pH that occur during the growth cycle in batch cultures. Data presented in the present paper indicate that provision of an external pH control (pH-stat) makes it possible to grow cell lines initiated from Ipomoea purpurea and Glycine max with ammonium as the only nitrogen source. Furthermore, with ammonium hydroxide as the titrant for pH control, the level of ammonium in the medium can be kept at a selected level (combined pH-stat and ammonium-stat) thus providing a greater degree of control over nutrient concentrations during growth than has been possible heretofore.A culture of Ipomoea cells grown under pH-stat – ammonium-stat conditions was comparable in growth rate and other parameters with one grown in a medium containing both ammonium and nitrate without pH control. However, the controlled culture produced more cells per milliliter than the one without control, and these cells remained high in nitrogen (milligram per gram basis) while the nitrogen content of cells in the culture without control declined late in the growthperiod.

A large outbreak of foodborne salmonellosis on the Navajo Nation Indian Reservation, epidemiology and secondary transmission

In September 1974, the largest outbreak of foodborne salmonellosis ever reported to the Center for Disease Control--affecting an estimated 3,400 persons--occurred on the Navajo Nation Indian Reservation. The responsible agent was Salmonella newport and the vehicle of transmission was potato salad served to an estimated 11,000 persons at a free barbecue. The cooked ingredients of the potato salad had been stored for up to 16 hours at improper holding temperatures. The magnitude of the outbreak allowed us to study secondary transmission by calculating the rates of diarrheal illness during the 2 weeks following the outbreak in persons who did not attend the barbecue and by examining the results of stool cultures obtained after the outbreak. We found no secondary transmission. We conclude that a health official should monitor food preparation and service at large social gatherings and that person-to-person transmission of salmonellosis probably does not normally occur even in settings considered highly conductive to cross-infection.

Acid hydrolase activity during growth and encystment in Acanthamoeba castellanii

The activity and sedimentation of acid phosphatase (APase), acid deoxyribonuclease (DNase), and acid ribonuclease (RNase) were investigated throughout growth and encystment in Acanthamoeba castellanii. The activities/mg protein of all 3 hydrolases are high in young cultures and decrease to constant levels in postlog cells. The RNase activity/ameba decreases 50% during growth, whereas the activity/cell of both APase and DNase remains constant. The percent sedimentation at 20,000 g of all 3 enzymes gradually increases from about 40% in midlog to a plateau of 80% in postlog cells. During encystment, the sedimentation behavior of RNase differs from that of APase and DNase. Encystment is characterized by a differential decrease in the activity/cell of the 3 hydrolases, with RNase decreasing most rapidly and APase least rapidly. APase is unique in that a transient increase of its specific activity is noted during encystment, even though its activity/cell is decreasing.

Growth of plant cell (Ipomoea) suspension cultures at controlled pH levels

Suspension cultures of a plant cell line initiated from Ipomoea sp. root tissue were grown in defined medium at controlled pH levels of 4.8, 5.6, 6.4, and 7.1 with ammonium and nitrate as the nitrogen sources. Biomass yield was less at pH 4.8 and 7.1 than at the intermediate pH levels. At pH 7.1, this resulted from the inability of the culture to utilize nitrate. At pH 4.8, the cause of the low yield was not apparent but was probably related to a less efficient utilization of sucrose.The ability of the cells to utilize ammonium increased with increasing pH, with a possible maximum at pH 6.4. The ability to utilize nitrate decreased with increasing pH and was essentially zero at pH 7.1. At pH 4.8, ammonium was released into the medium during part of the growth cycle, indicating that the rate of nitrate reduction exceeded the rate of incorporation of the ammonium thus formed.Utilization of nitrate was not inhibited by the presence of ammonium.

Effect of ammonium on growth of plant cells (Ipomoea sp.) in suspension cultures

Maintenance of the ammonium level in batch cultures of a plant cell line initiated from Ipomoea root tissue resulted in cells with a higher nitrogen content and a greater total accumulation of nitrogen in the cells. Utilization of nitrate was not suppressed. The increased supply of ammonium did not, by itself, increase the yield of dry cells, but it did permit a twofold or greater increase in cell yield when sucrose was added subsequently.Supplementary feeding of ammonium and sucrose to a batch culture that had exhausted the initial supply of ammonium rapidly returned the cells to a state of high nitrogen content, favored further utilization of nitrate, and greatly increased cell yield.These results are discussed in terms of growth phases. The presence of ammonium in the medium appeared to induce and maintain a growth phase characterized by a high nitrogen level in the cells. After the ammonium supply was depleted a second phase occurred, characterized by a rapid increase in dry weight without proportional accumulation of nitrogen. This second phase was not caused by a limiting rate of nitrate utilization, nor was it directly related to observed pH changes. We conclude that the two phases relate to the presence and absence of ammonium in the medium.

Growth of suspension cultures of plant cells (Ipomoea sp.) at various temperatures

Studies on the growth of batch suspension cultures of a plant cell line, initiated from Ipomoea sp. root explants, at temperatures ranging from 15 to 34 °C are reported. Maximum growth of cultures of this cell line occurred between 25 and 32 °C, with temperature variations within this range having little effect on growth rates based on dry cell yields. Cultivation at 20 °C substantially reduced the growth rate. However, cells grown at 20 °C failed to grow on transfer to fresh medium at 20 °C. Thus cultivation at suboptimum temperatures is not a satisfactory method for routine maintenance of the suspension culture.

Parameters for growth measurement in suspension cultures of plant cells

Well-adapted cells, which had been initiated from root tissue of Ipomoea and of Daucus carota, were grown in 7.5-liter stirred-jar fermenters, and both the cells and media were analyzed for major components at intervals during the growth period. Controlled variables included the size of inoculum, the amount of sucrose, and the source and amount of nitrogen in the media.The data obtained indicate that there are two distinct growth phases in the development of batch cultures of these cell lines. The first, which we term "cytoplasmic growth phase," begins immediately upon addition of inoculum to fresh medium and is characterized by a high rate of nitrogen uptake and metabolism relative to the increase in cell dry weight. The second, or "maturation phase," is characterized by large increments in dry weight and total cell carbohydrate relative to the increments in cell nitrogen. It is suggested that the classical lag, log, and stationary phases of bacterial growth could apply only to the early hours of cytoplasmic growth, if indeed they are relevant at all.

Metabolic rates for major nutrients in suspension cultures of plant cells

Well-habituated cells, which had been initiated from root tissue of Ipomoea sp. and kept in suspension culture for more than 2 years, were grown in 14-liter stirred-jar fermenters in complex media containing casein hydrolysate. Samples were taken at 12-h intervals, and both cells and media analyzed for major constituents. Polynomial functions of time were fitted, by least squares, to these data, and the rate of disappearance or accumulation (medium and cells, respectively) of the major components was calculated by dividing the first derivative of these functions by the corresponding dry cell weight. The results indicate that growth of these cultures involved a sequence of activities such that the culture as a whole, during the period of rapid increase in cell yield, progressed from one containing predominantly dividing cells with a high rate of nitrogen anabolism to one containing predominantly "maturing" cells with a proportionately higher rate of carbohydrate anabolism. Increasing the nitrogen content of the medium affected the metabolic rates and the apparent net growth rate to only a minor extent, but did alter cell composition.

Two peroxidases isolated from kidney bean cell suspension cultures

Two peroxidases, isolated from filtrates of suspension cultures of a cell line derived from red kidney bean (Phaseolus vulgaris) were purified 145- and 72-fold respectively. The two enzymes were quite similar in many of their properties and both were typical plant peroxidases. They differed markedly, however, in their molecular weights (estimated by gel filtration). The molecular weight of peroxidase I was 30 000 whereas that of peroxidase II was only 6000.

Isolation and preliminary characterization of an extracellular protease of Cytophaga sp

The extracellular protease(s) of Cytophaga sp. is present naturally as a complex with acidic polysaccharides of the slime layer. The protein was separated from the slime by selective precipitation of the polysaccharide with a cationic detergent and the enzyme was purified about 100-fold by precipitation with alcohol and by chromatography on DEAE-cellulose. Inhibitor studies indicated that this alkaline protease was not of the trypsin/chymotrypsin type. Ca2+ had a strong stabilizing effect on the enzyme. The complex of basic protein (enzyme) and acidic slime polysaccharides has led to the conclusion that the enzyme is perhaps not truly extracellular but rather is surface bound. The slime layer would appear to have a role in attaching the bacterial cells to insoluble substrates as well as ensuring that degradative enzymes are kept in close contact with the substrate.

Lignofibrils on the external cell wall surface of cultured plant cells

Small strands and bundles of strands extend from the outside surface of suspension-cultured cells of Daucus, Ipomoea, and Phaseolus into the medium. This fibrous cell coat is present in all samples from various growth stages but appears to increase in quantity in the order Ipomoea < Phaseolus < Daucus. The bundles are often many microns in length and display great variation in frequency, size, and form. Identification of the composition of the strands and bundles as lignin is consistent with the following observations: alkaline nitrobenzene oxidation of the strands to compounds which resemble monomers of wood lignin; resistance of the strands to pronase, trypsin, pectinase, and lipase; strong irreversible adsorption of heavy metals; deposition of silver granules by treatment with silver nitrate-hexamine reagent; extraction of the bundles with aqueous dioxane (Björkman procedure); presence in quantity of a structured form of Klason lignin; and existence of material giving a positive test with the Wiesner reagent. Large individual strands (lignofibrils) from Phaseolus show the form of a flat ribbon with very thin branches at irregular intervals. This form does not vary with preparatory techniques, although its electron opacity does. Intercellular spaces display considerable structure and sometimes contain sheets of fibrillar material merging with both the middle lamella between the cells and the surface bundles facing the medium. These sheets are probably another form of association of the lignofibrils. It is suggested that natural fibrous lignin may be a much commoner component of plant tissue than suspected hitherto.

A fermenter for plant cell suspension cultures

A conical glass V-fermenter for plant cell suspension cultures is described. This V-fermenter has proved useful for the production of biomass and metabolic products. It also is ideally suited for the preparation and maintenance of actively growing cultures to be used as inocula for shake flasks and fermenters. An outline of the procedure for isolating and "conditioning" plant cell suspension cultures is presented.