Studies on orthocephalization. 10. Behaviour of the visceral part of the rat head during the first 14 days after gestation

The present paper considers the significance of interosseous flexions of the palatal complex in the process of orthocephalization of the rat skull between birth and 7 d p.n. The study is based on a sample of 90 rats divided into 4 age groups, i.e. 0, 4, 7, and 14 d. These rats have been X-rayed, and their photographs subsequently analysed. During the studied period, the constituents of the bony palate, i.e. the horizontal part of the palatine bone, the palatal process of maxilla and the palatal part of premaxilla, increase markedly in length, but with individual differences in growth rate. There is, in the period, a marked decrease in angulation between the cranial base and the palatal plane. This means that the rat skull becomes more orthocranial. There is also a straightening (orthopalatalization) of the palate, as the angle between maxilla and premaxilla becomes more obtuse, and a marked decrease in angulation between the palatine bone and the cranial base. The patterns of angular changes suggest that the process of orthocephalization in the period between birth and 14 d p.n. primarily is a result of an upwards rotation of the palatine bone relative to the cranial base, while interosseous deflections in the palate only play a minor role.     

Effects of peroxide and catalase on near ultraviolet radiation sensitivity in Escherichia coli strains

The role of peroxide and catalase on NUV radiation sensitivity was examined in two repair competent E. coli strains, AB1157 and B/r. Exponential phase B/r is considerably more sensitive to NUV radiation than exponential phase AB1157. However, resistance to 5 mmol dm-3 H2O2 was induced in both AB1157 and B/r by pretreating growing cells with 30 mumol dm-3 H2O2. Pretreatment also induced resistance to broad-band NUV radiation in these strains. The addition of catalase to the post-irradiation plating medium increased survival to the same extent as that provided by pretreatment with 30 mumol dm-3 H2O2, in both strains. The NUV radiation sensitivity seen in B/r does not appear to be due to a deficiency in enzymes that scavenge H2O2, as a catalase deficient mutant, E. coli UM1, is more resistant to NUV radiation than B/r. Also, assays for H2O2 scavenging ability show little difference between AB1157 and B/r in this respect. Two hypotheses are put forward to account for the sensitivity of exponential phase B/r. Whilst it is apparent that peroxides and catalase do have a role in NUV radiation damage, it is clear that other factors also influence survival under certain conditions.     

Species specificity of bacterial palindromic units

We described previously a family of dispersed palindromic sequences highly repeated in Escherichia coli and Salmonella typhimurium genomes. These sequences, called PU (palindromic units), are located outside structural genes. We report here observations suggesting that PU may have a role in bacterial speciation.     

Properties of the 3′-phosphoadenosine-5′-phosphosulfate (PAPS) synthesizing systems of brain and liver

Chromatography of brain and liver 100,000g supernatants over HPLC molecular sieve columns revealed striking differences in the molecular weight distribution of ATP-sulfurylase and APS-kinase of the two tissues, pointing to different enzymic species for both enzymes in brain and liver. This was further substantiated by kinetic characterization of the two enzymes of both tissues. APS-kinase of liver is allosterically activated by ATP, while the brain enzyme is not. ATP-sulfurylase of brain is activated at high, but still physiological concentrations of ATP. Brain ATP-sulfurylase is inhibited by phenylalanine.     

HIV testing: changing trends at a clinic for sexually transmitted diseases in London.

Trends in human immunodeficiency virus (HIV) counselling and antibody testing at a London clinic for sexually transmitted diseases showed substantial changes over a 12 month period. From around 100 a month in the summer of 1986 the numbers of people attending rose substantially to 276 in October 1986 and 475 in November at the time of the campaign in the popular press. They rose further still, to 700, at the time of AIDS (acquired immune deficiency syndrome) week in March 1987. In April they fell to the levels seen six months previously. Apart from this increase in overall numbers the proportions of women and heterosexual men who were seen increased.     

Comparison of sequences from the malB regions of Salmonella typhimurium and Enterobacter aerogenes with Escherichia coli K12: A potential new regulatory site in the interoperonic region

Summary The malE and malK genes from Salmonella typhimurium, and the MalEFG operon and a portion of malK from Enterobacter aerogenes were cloned and sequenced. Plasmid-borne malE genes from both species and the malF and malG genes from E. aerogenes were expressed normally in Escherichia coli, and their products function in maltose transport. This shows that the malB products from the three species are interchangeable, at least in the combinations tested. The general genetic organization of the malB region is conserved. Potential binding sites and distances between them are highly conserved in the regulatory intervals. An unexpected conserved region was detected, which we call the U box, and which could be another target for a regulatory protein. This hypothesis is supported by the presence of the U box in the regulatory, region of the pulA-malX operon in Klebsiella pneumoniae. The intergenic region between malE and malF from S. typhimurium and E. aerogenes, contains inverted repeats similar to the palindromic units (PU or REP) found at the same location in E. coli. The predicted amino acid sequence of the encoded proteins showed 90% or more identity in every pairwise comparison of species.     

Quantity and Kinetic Properties of Ribulose 1,5-Bisphosphate Carboxylase in C3, C4, and C3-C4 Intermediate Species of Flaveria (Asteraceae)

The kinetic properties of ribulose 1,5-bisphosphate carboxylase(RuBPC) appear to have been modified during evolution of photosynthesisto adjust to changes in substrate availability. C₄ plants areconsidered to have a higher concentration of CO₂ available toRuBPC than C₃plants. In this study, the K_m(CO₂ and catalyticcapacity (k_cat) of RuBPC and the ratio of RuBPC protein to totalsoluble protein from several Flaveria species, including C₃,C₃-C₄ intermediate, and C₄ species, were determined. The C₃and intermediate species had similar K_m(CO₂) values while theC₄ species on average had higher K_m(CO₂) values. The mean ratioof K_cat/K_m for species of each group was similar, supportingthe hypothesis that changes in K_m and K_cat, are linked. Theallocation of total soluble protein to RuBPC was lowest in theC₄ Flaveria species, intermediate in the C₃-C₄ species, andhighest in the C₃ species. The results suggest that during evolutionof C₄ photosynthesis adjustments may occur in the quantity ofRuBPC prior to changes in its kinetic properties. (Received January 4, 1989; Accepted April 11, 1989)     

Fluorometric analysis of an attempt to reclaim ischemic flaps in rats with Fluosol

An experiment was designed to answer two questions as they apply to random skin-flap survival: Is there a therapy that can improve random skin-flap survival when given postoperatively? And if so, when does one start such a therapy? Fluosol-DA 20% (Fluosol) has increased random skin-flap survival when given preoperatively in our laboratory. An experiment was devised to see if it could rescue failing flaps. One-hundred Sprague-Dawley rats were divided into a control (N = 25) and five experimental groups (N = 15). All had 10 X 13 cm reverse McFarlane random flaps raised and reinset. The experimental groups underwent hemodilution with either Ringer's lactate or Fluosol at 4, 8, and 12 hours after flap elevation. All were kept in 50% oxygen for 72 hours postoperatively. The flaps and their corresponding necrotic areas were measured on day 7. As to when to institute a therapy, we simultaneously evaluated the use of a microfluorometer as a monitor of flap survival. Analysis of flap survival showed little difference between control and experimental Ringer's lactate or Fluosol groups. Analysis of the microfluorometric data led to the following points. First, as a monitor of flap viability, it is limited by a lack of specificity and sensitivity. Second, comparison of the data from portions of the flap destined to live with those destined to die suggests that it may not be failure of circulatory inflow that leads to flap death.     

Standardized method for evaluation of hand disinfection by surgical scrub formulations

A standardized protocol for the evaluation of hand disinfection by surgical scrub formulations was applied to volunteers in a multicenter trial. Povidone iodine (PVI), chlorhexidine (CHX), and a nonmedicated soap (NMS) were tested. The scrubbing procedure involved three daily hand washings for five consecutive days; surviving bacteria were counted daily after being collected in a suitable neutralizing solution. Immediate efficacy (IE), cumulative efficacy (CE), and remanent effect (RE) were calculated by reference to the control hand. Statistical analyses of IE, CE, and RE showed significant differences among the three scrub formulations. IEs of PVI and CHX were equivalent and different from IE of NMS; CE and RE of CHX were higher than those of PVI and NMS. On the basis of the statistical analysis, the population size required for further studies aimed at detecting significant differences between surgical scrub formulations could be estimated.     

Coordinate replication of dispersed repetitive sequences in Physarum polycephalum

The synchronous macroplasmodial growth phase of the slime mould Physarum polycephalum was used to study the in vivo replication of large chromosomal DNA segments. Newly replicated DNA was isolated at various points in S-phase by its preferential association with the nuclear matrix. This DNA was then used to probe cosmid clones of the Physarum genome. The results indicate that certain dispersed repetitive sequences in the genome are coordinately replicated. The observed pattern of replication may be due either to the presence of a replication origin within each repetitive sequence or to the systematic arrangement of these sequences around a replication origin. The latter appears more likely since the repetitive sequences are probably not randomly scattered within the genome.