Closing in on maximum yield of chlorophyll fluorescence using a single multiphase flash of sub-saturating intensity.

Estimation of the maximum chlorophyll fluorescence yield under illumination, or Fm', by traditional single saturation pulse (SP) methodology is prone to underestimation error because of rapid turnover within photosystem (PS) II. However, measurements of fluorescence yield during several single pulses of variable intensity describes the irradiance dependence of apparent Fm', from which estimates of Fm' at infinite irradiance can be derived. While such estimates have been shown to result in valid approximations of Fm', the need to apply several single pulses limits its applicability. We introduce a novel approach that determines the relationship between apparent Fm' and variable irradiance within a single ∼1 s multiphase flash (MPF). Through experiments and simulations, we demonstrate that the rate of variation in irradiance during an MPF is critical for achieving quasi-steady-state changes in the proportions of PSII acceptor side redox intermediates and the corresponding fluorescence yields, which are prerequisites for accurately estimating Fm' at infinite irradiance. The MPF methodology is discussed in the context of improving the accuracy of various parameters derived from chlorophyll fluorescence measurements, such as photochemical and non-photochemical quenchings and efficiencies. The importance of using MPF methodology for interpreting chlorophyll fluorescence, in particular for integrating fluorescence and gas exchange measurements, is emphasized.

The gel microdrop secretion assay: Identification of a low productivity subpopulation arising during the production of human antibody in CHO cells.

The long-term stability of high-level expression is the mostimportant factor to consider when choosing cell lines for the expression of recombinant proteins. Declining volumetricyields in large-scale fermentation can be caused by changes affecting the cell population as a whole such as loss in viability, depletion of nutrients or accumulation of metabolites affecting cell growth. Alternatively, geneticinstability may lead to the outgrowth of a less productive,metabolically favored sub-population. Currently a variety ofparameters are measured to monitor the condition of cells infermenters including glucose uptake, lactate accumulation andoxygen consumption; in addition, periodic viable cell countsallow the determination of the growth rate and viability of the population. All of these methods measure the condition ofthe cell population as a whole and changes must involve a significantly large proportion of the total culture in orderto be detectable. Here we report on a method that allows theevaluation of the productivity of individual cells. Using the gel microdrop secretion assay, we detected the appearance ofa sub-population of cells with lower productivity. Subsequentanalysis of the culture confirmed the existence of lower productivity cells with a lower vector copy number. Therefore,the single cell secretion assay proved to be a rapid method todetect and isolate a low productivity variant of the producer cell line.

Reducing bacterial aerosol contamination with a chlorhexidine gluconate pre-rinse.

The authors compared the effects of chlorhexidine gluconate, an antiseptic mouthwash with essential oils and water on the bacterial aerosol contamination generated by an air polishing device. Patients rinsed with one of the three solutions before treatment. Bacterial counts collected during the treatment indicate that the chlorhexidine pretreatment rinse was significantly more effective than the other solutions in reducing bacterial aerosols.

Complex-type N-linked oligosaccharides of gp120 from human immunodeficiency virus type 1 contain sulfated N-acetylglucosamine.

The major envelope glycoproteins gp120 and gp41 of human immunodeficiency virus type 1, the causative agent for human AIDS, contain numerous N-linked oligosaccharides. We report here our discovery that N-acetylglucosamine residues within the complex-type N-linked oligosaccharides of both gp120 and its precursor, gp160, are sulfated. When human Molt-3 cells persistently infected with human T-cell leukemia virus IIIB were metabolically radiolabeled with 35SO4, gp160, gp120, and to some extent gp41 were radiolabeled. The 35SO4-labeled oligosaccharides were quantitatively released by N-glycanase treatment and were bound by immobilized Ricinus communis agglutinin I, a lectin that binds to terminal beta-galactosyl residues. The kinetics of release of sulfate upon acid hydrolysis from 35SO4-labeled gp120 indicate that sulfation occurs in a primary sulfate ester linkage. Methylation analysis of total glycopeptides from Molt-3 cells metabolically radiolabeled with [3H]glucosamine demonstrates that sulfation occurs at the C-6 position of N-acetylglucosamine. Fragmentation of the gp120-derived 35SO4-labeled glycopeptides by treatment with hydrazine and nitrous acid and subsequent reduction generated galactosyl-anhydromannitol-6-35SO4, which is the expected reaction product from GlcNAc-6-sulfate within a sulfated lactosamine moiety. Charge analysis of the [3H]galactose- and [3H]glucosamine-labeled glycopeptides from gp120 and gp160 indicates that approximately 14% of the complex-type N-linked oligosaccharides are sulfated.

gp160 of HIV-I synthesized by persistently infected Molt-3 cells is terminally glycosylated: evidence that cleavage of gp160 occurs subsequent to oligosaccharide processing.

The envelope glycoprotein of HIV-I in infected, cultured human T cells is synthesized as a precursor of apparent Mr 160 kDa (gp160) and is cleaved to two glycoproteins, gp120 and gp41, which are the mature envelope glycoproteins in the virus. Neither the temporal and spatial features of glycosylation nor the oligosaccharide processing and proteolytic cleavage of the envelope glycoprotein are well understood. To understand more about these events, we investigated the glycosylation and cleavage of the envelope glycoproteins in the CD4+ human cell line, Molt-3, persistently infected with HIV-I (HTLV IIIB). The carbohydrate analysis of gp160 and gp120 and the behavior of the glycoproteins and glycopeptides derived from them on immobilized lectins demonstrate that both of these glycoproteins contain complex- and high-mannose-type Asn-linked oligosaccharides. In addition, the N-glycanase-resistant oligosaccharides of gp120 were found to contain N-acetyl-galactosamine, a common constituent of Ser/Thr-linked oligosaccharides. Pulse-chase analysis of the conversion of [35S]cysteine-labeled gp160 showed that in Molt-3 cells it takes about 2 h for gp120 to arise with a half-time of conversion of about 5 h. At its earliest detectable occurrence, gp120 was found to contain complex-type Asn-linked oligosaccharides. Taken together, these results indicate that proteolytic cleavage of gp160 to gp120 and gp41 occurs either within the trans-Golgi or in a distal compartment.

Transcellular transactivation by the human immunodeficiency virus type 1 tat protein.

The human immunodeficiency virus type 1 (HIV-1) transactivator (tat) protein produced in one cell activated HIV-1 promoter-directed gene expression in a second cell, provided the cells were in direct contact with one another. This observation suggests that the tat protein produced in HIV-1-infected cells has a physiological effect on neighboring cells.

The maternal erotic countertransference.

This paper reviews literature on countertransference erotism and perversion, and offers our conception of the maternal erotic countertransference. We stress that sado-masochistic issues are not only issues of aggression, but represent pre-oedipal erotism as well. The analyst's struggle with these issues may contribute to a perverse misalliance instead of a creative coupling. It is typical of the perverse misalliance that it contains a refusal to participate, with all the attendant disinterest and deadness and lack of creativity usually associated with that condition. We have emphasized two keys to springing the analyst from the deadlocks of such paralysing countertransferences, thereby opening access to the creative use of both maternal erotic transference and countertransference. First, is the analyst's ability to view herself or himself as maternally erotic; and second, is the analyst's ability to experience, contain and make accessible to analysis the patient's potential erotism, including its perverse aspects.

The maternal erotic transference.

After reviewing literature on gender and erotic transferences, which have often been treated as primarily problematic, this paper offers a positive and transformational view of aspects of what is called the maternal erotic transference (MET). Rooted in mother and baby's earliest sensual contacts, it manifests in concrete transferences to the real parts of the body of the therapist; its expressions are typically inhibited as preverbal and/or defended against out of shame and fear of humiliation. Analysts of both genders who have access to their own maternal erotic countertransferences and their patients' matching transferences may enable their patients' acceptance of and immersion in the maternal erotic transference in its loving and sado-masochistic permutations and thus foster the making of a sense of wholeness, and connectedness to living. Experienced thus, MET may herald the transition in the analysis from a dyadic to a triadic oedipal phase animated by accessible pre-oedipal aggressivity and sensuality.

Toxicologic evaluation of cefamandole nafate in laboratory animals.

The safety of cefamandole nafate in laboratory animals was evaluated in six species. The acute toxicity of cefamandole after intravenous or subcutaneous administration was similar to that of cephalothin sodium. The subacute and chronic toxicity of cefamandole was studied in rats and dogs for periods of two weeks to six months at doses of 250--1,000 mg/kg per day in rats and 125--1,500 mg/kg per day in dogs. No evidence of significant systemic toxicity was observed in these studies. There were, however, various degrees of local injury at the injection sites that resulted in slight decreases in hemoglobin, hematocrit, and red blood cell counts in the animals in which injury at the injection site was most severe. Studies of reproduction in rats and mice indicated that cefamandole nafate had no teratogenic effects and no adverse effects on fertility, gestation, or growth of offspring. Comparative studies of nephrotoxicity in rabbits demonstrated that the nephrotoxicity of cefamandole nafate was considerably less than that of cefazolin.

Aspects of the pharmacology and toxicology of tobramycin in animals and humans.

The pharmacology and toxicology of tobramycin in animals and humans are reviewed. After intramuscular and intravenous administration, tobramycin diffuses throughout most body tissues and tissue fluids. Therapeutic concentrations can be obtained by intravitreal or intradural injections. Dogs tolerate intracisternal doses of 0.2 mg/kg without adverse reaction. The half-life of tobramycin in cochlear fluid of guinea pigs and in renal tissues of rats is significantly longer than the serum half-life in these species and is reflected in the ototoxic and nephrotoxic potential of tobramycin and other aminoglycosides. In man, the serum half-life of tobramycin is 2 hr; renal clearance, apparent volume of distribution, and recovery from urine are similar to those parameters for gentamicin. The serum half-life in neonates in prolonged (4.5-8.7 hr). Concentrations of tobramycin in serum are effectively reduced by hemodialysis, but peritoneal dialysis is less efficient in elimination of the antibiotic. Tobramycin crosses the placenta and is concentrated in the kidney and urine of the fetus.

New synthetic antibacterial compound, 1-(2-hydroxyethyl)-3-nitro-4-pyrazole carboxamide.

A series of 3-nitropyrazole compounds represent a new class of synthetic antibacterial agents. One member of this series, 1-(2-hydroxyethyl)-3-nitro-4-pyrazolecarboxamide, exhibited an antibacterial spectrum similar to that of nitrofurantoin. The inhibitory concentrations of this nitropyrazole were lower than those required for nitrofurantoin. Single oral doses of 20 mg/kg resulted in peak nitropyrazole concentrations of 5.8 and >1,000 mug/ml in mouse blood and urine, respectively. In dogs, 87% of a 10 mg/kg oral dose was recovered in urine during a 24-h period with a peak serum concentration of 13.6 mug/ml. This nitropyrazole was highly effective against experimental bacterial infections in mice. The low acute toxicity in mice, rats, or dogs and significant antibacterial activity lead to the conclusion that further evaluation of this compound is warranted.