Aryl hydrocarbon hydroxylase induction in mouse liver cells--relationship to position in the cell cycle

The inducibility of aryl hydrocarbon hydroxylase (AHH) by benzo[a]-pyrene (BaP) has been studied in synchronously grown cultures of mouse liver cells. These cells (NMuLi cl 8) have low basal levels of AHH which can be induced greater than 100-fold by BaP. Cells were synchronized in G1(G0) by serum starvation and in S by release from serum starvation in combination with excess thymidine. When released from G1(G0) by replating at lower cell density in fresh medium with 20% serum, cells began entering S with a lag of 12 h. Addition of BaP (1 microgram/ml) 8 h before serum stimulation, at the time of stimulation or 7.5 h after stimulation all gave similar induction kinetics: the AHH activity peaked as the cells began entering S regardless of when the BaP was added. Cells blocked in various parts of S by excess thymidine were inducible for AHH activity as efficiently as cells moving through S and into G2. These results indicate that the inducibility of AHH is greater when cells are actively proliferating and may be a contributing factor to why growing cells are more sensitive to mutagenesis and transformation than quiescent cells.     

Microbial metabolism of carbon monoxide in culture and in soil.

Nocardia salmonicolor readily oxidized CO to CO2. Slight activity was found among species of Actinoplanes, Agromyces, Microbispora, Mycobacterium, and other nocardias, and no oxidation was detected in the algae, fungi, and other bacteria tested. Carbon monoxide was oxidized rapidly to CO2 in the dark in two soils incubated in air or under flooded conditions, but little of the 14C from 14CO was incorporated into the organic fraction of these soils. The reaction was microbial because appreciable CO was not converted to CO2 in autoclaved or gamma-irradiated soil. Heating the soil for 25 min at 70 degrees C destroyed its CO-oxidizing activity. The incorporation of 14CO2 into the cells of microorganisms in soil and soil suspension was not enhanced by incubating the samples in the presence of CO, suggesting that CO oxidation was not the result of autotrophic metabolism. The oxidation of 17 mu 1 of CO per liter in the head space was nearly complete in 6 h in soil incubated in air or anaerobically.     

Sedimentation characteristics and effect of molasses concentration and medium supplementation on the ethanol productivity of an ethanol tolerant palm wineSaccharomyces

Summary Sedimentation rates ranging from 58.82 to 93.10% were recorded for six palm wineSaccharomyces yeast isolates. Isolates S, J and A₃, gave values of 90.00, 91.95 and 93.10% respectively compared to 81.54% for a standard lager beer yeast. Fermentation of unclarified molasses medium 10–30° Brix with isolated J gave ethanol productivity of 74.35-67.07%. Soyabean, groundnut or castor oil seed meal supplements significantly enhanced ethanol productivity in all the molasses media.     

Identification and characterization of membrane cofactor protein of human spermatozoa.

Membrane cofactor protein (MCP) regulates C activation by serving as a cofactor for the cleavage of C3b and C4b by the serine protease factor I. An MCP-like molecule on the inner acrosomal membrane of human spermatozoa has been characterized. Three mAb and a rabbit polyclonal antibody against MCP recognized the sperm protein. On SDS-PAGE, it migrated as a single band with a molecular mass of 38,000 and 44,000 Da under nonreducing or reducing conditions, respectively. The molecular mass was 10,000 to 20,000 Da less than the two forms of MCP expressed on others cells. The electrophoretic pattern, by one- and two-dimensional gel analysis, and the isoelectric point profile (4.5 to 5.0) of the sperm protein were similar among multiple individuals. In contrast to MCP of other cells, digestion with endoglycosidases did not alter either the m.w. or the pI of the protein, suggesting that it is a poorly or nonglycosylated form of MCP. The solubilized sperm protein bound C3 with broken thioester bond to Sepharose and possessed cofactor activity for factor I-mediated cleavage of C3 with the broken bond. A mAb that blocks the regulatory function of MCP inhibited the cofactor activity of the sperm lysate. Thus, the sperm protein is an antigenic and functional homologue of MCP but has the distinct structural features of a lower m.w. and an apparent lack of glycosylation. MCP may play an essential role in the survival of the acrosome-reacted spermatozoa by modulating C activation in the female genital tract.     

Hypothalamic Grafts Induce the Recovery of Lordosis in Female Hamsters with Lesions of the Ventromedial Hypothalamus

Previous studies have documented the ability of neural grafts to stimulate the recovery of lordosis from neurochemical deficits. However, it was unclear if grafts also could reverse deficits in lordosis caused by lesions at critical points in the neural circuit controlling this response. To address this question, female hamsters were subjected to unilateral lesions of the ventromedial hypothalamus (VMN), a structure well known for its mediation of hormonal effects on lordosis. The effects of these lesions were described by noting the ability of manual stimulation of one flank to reinstate a deteriorating lordosis response. Consistent with past results, unilateral VMN lesions decreased responsiveness to stimulation of just the contralateral flank. Females showing such lateralized decrements then received control treatments or implants into the lesioned area of basal hypothalamic tissue from a neonatal male or female hamster. Approximately 1 month later, tests of lordosis reinstatement by ipsi- or contralateral manual stimuli were repeated. Whereas lateralized decrements in responsiveness persisted in control subjects, implants of tissue from male or female neonates led to reliable improvements in lordosis, reversing the lesion-induced decrease in contralateral responsiveness. The mechanism responsible for this change is unclear, but could involve an elevation in a lordosis-facilitating neuromodulator. Alternatively, it could depend on the reinforcement or replacement of neural circuits for lordosis, possibly including those that connect the two VMNs with each other or with the periaqueductal gray of the midbrain.