Molecular evolution of the carbonic anhydrase genes: Calculation of divergence time for mouse carbonic anhydrase I and II

Summary A cDNA clone in pBR322 that cross-hybridizes with a mouse carbonic anhydrase form II (CAII) probe has been sequenced and identified as mouse carbonic anhydrase form I (CAI). The 1224-base-pair clone encodes the entire 260-amino-acid protein and appears to contain an Alu-like element in the 3 untranslated region. The deduced amino acid sequence exhibits 77% homology to human CAI and contains 17 of the 20 residues that are considered unique to and invariant for all mammalian CAI isozymes. The results of a detailed comparison of the nucleic acid sequences spanning the coding regions of mouse CAI and rabbit CAI have been used to calibrate an evolutionary clock for the carbonic anhydrases (CAs). These data have been applied to a comparison of the mouse CAI and CAII nucleic acid sequences to calculate the divergence time between the two genes. The divergence-time calculation provides the first estimation of the evolutionary relationship between CAs based entirely on nucleotide sequence comparison.     

Chromosomal organization of the herpes simplex virus genome during acute infection of the mouse central nervous system.

After corneal inoculation, herpes simplex virus type 1 replicates in the mouse eye, trigeminal ganglia, and brainstem, producing first an acute and then a latent infection. Previous work from this laboratory focused on the structure of the viral DNA in this system. We have now examined the structure of the viral genome at the chromosome level by using micrococcal nuclease digestion. Studies with disaggregated cell preparations made from the brainstems of acutely infected mice show that the majority of the viral DNA is in a nonnucleosomal form; however, a nucleosomelike fraction was also consistently detected. A similar result was obtained for viral DNA in herpes simplex virus type 1-infected C1300 (clone NA) neuroblastoma cells (a neuronal cell line).     

Albumin is required to support the acrosome reaction but not capacitation in mouse spermatozoa in vitro

Albumin was required specifically for penetration of the zona pellucida (less than 10% of eggs fertilized in the absence of albumin), but was not required for capacitation. A similar rate of capacitation was observed in the presence of albumin at concentrations ranging from 30 to 1 mg/ml, while a slightly slower rate was observed in the presence of 0.25 and 0.1 mg albumin/ml. In the absence of albumin, capacitation occurred at a rate which lagged behind that of the albumin-incubated counterparts by about 30 min; once capacitated, the addition of albumin promoted rapid sperm penetration. In albumin-free media (+/- the macromolecule PVA), sperm motility was frequently reduced, with fewer cells exhibiting hyperactivated motility, but improvements were observed after introduction of albumin. Acrosome loss was significantly lower in the absence of albumin, but within 5 min of its addition at concentrations ranging from 30 to 0.1 mg/ml to capacitated sperm suspensions, acrosome loss was stimulated and reached levels similar to those seen in control samples. Therefore, albumin can trigger the acrosome reaction in capacitated spermatozoa. It appears to act by assisting in the removal of a surface-associated inhibitory component, the presence of which stabilizes the sperm membranes and inhibits the acrosome reaction.     

Intermediate filament structure

In a previous communication (Biosci. Rep. 3, 517–525, 1993) we described quantitative X-ray diffraction studies of -keratin which were shown to be consistent with the presence of finite arrays of repeating units, successive arrays being set down at axial intervals of 470 Å. In addition the axial interval between repeating units in an array was shown to be 197.9 Å. It was suggested that this could most readily be explained by supposing that a surfacelattice was present which contained a dislocation along a helical path with unit heighth = 470 Å and unit twist |t| = 49.1° . The number of repeating units was shown to be in the range 7–9. With 7 repeats the mismatch of the lattice along the dislocation is small and this choice was used to develop a detailed model for the filament. Subsequent studies of molecular interactions have shown however that the coiled-coil rope segments in the rod domain of the molecule are most probably oriented parallel to the dislocation, and so minimization of lattice mismatch may be less important than originally supposed. In the present communication it is shown that the choice of 8, rather than 7, for the number of repeating units yields a model which is more compatible with estimates of the linear density and also provides the basis for a general model for polymorphism in intermediate filament lattices.     

Effect of upper airway carbon dioxide on ventilation and blood gases in the awake pony

Carbon dioxide concentrations were increased during expiration in the upper one-half of the trachea, pharynx, and nasal sinuses to determine if elevation of upper airway CO2 would alter breathing or arterial blood gases in the awake pony. Carbon dioxide (100%) was injected into the midcervical trachea via a chronically implanted transcutaneous cannula during the first part of the animal's expiration. This maneuver elevated upper airway expiratory CO2 concentrations but prevented any exogenous CO2 from entering the lung and being absorbed into the arterial blood. Twelve experiments were performed on six ponies in which upper airway CO2 was elevated 2, 4, and 6% above the normal expired CO2 concentrations. Tidal volume increased in a dose dependent manner during upper airway CO2 exposure, but total ventilation was unchanged from base-line measurements made while the animal breathed room air. Arterial Po2 also increased during upper airway CO2 administration, reaching a mean value 6 Torr (1 Torr = 133.322 Pa) greater than the base-line values at the +6% CO2 exposure. We conclude that upper airway CO2 exposure alters breathing pattern slightly (increases tidal volume) and increases arterial PO2 in the awake pony.     

The effects of a settled industrial–domestic sewage works effluent from percolating filters on the survival and growth of various stages of rainbow trout, Salmo gairdneri (Richardson)

Comparisons were made of the mortality, growth and condition factor over a 50-day period of eleutheroembryos, alevins, 2-month fry, 4-month fry and 1 + rainbow trout, Salmo gairdneri , in water of three qualities–Birmingham tap-water, 50% and 100% settled effluent from percolating filters (Minworth Effluent Treatment Works) when dissolved oxygen levels were maintained near 100% ASV.
There was no significant mortality among life stages in control tap-water but the LT50 values of life stages in both 50% effluent and 100% effluent revealed significant differences. Inter-treatment comparisons showed similar mortalities of eleutheroembryos, of 2-month fry and of 1 + fish in the three treatments but LT50 values of 4-month fry showed significant differences. Growth rates of 2-month and 4-month fry were suppressed in both effluents after 7 days and there was a significant deterioration in the K factor of these life stages after 14 days. Predicted toxicities (the sum of the proportions of the 48-h LC50 of the individual poisons to rainbow trout) were compared with the observed toxicity in 50% and 100% effluent. The relevance of in vivo testing in comparison to predictive techniques is compared.     

Seasonal variation of neural tube defects in Newfoundland and elsewhere

In Newfoundland, babies with anencephaly are conceived most often in January, and those with spina bifida in August. These and previous observations suggest that (1) seasonal fluctuations are greatest when the population frequency is neither very high nor very low, and that (2) the peak season for conception of anencephalic babies may occur in any season except August-November in various populations, whereas for spina bifida seasonal peaks are confined almost exclusively to May-August.