A spectroscopic study of metal ion and ligand binding to β-lactamase II

β-Lactamase II has two metal-binding sites. The electronic spectra of Cd(II)- and Co(II)-substituted β-lactamase II have been investigated. It is suggested that a thiol ligand is involved in metal binding at the first site. The stoichiometric dissociation constants for Co(II) binding to β-lactamase II were estimated to be 0.13 and 2.66 mM (pH 6.0, 4°C, 1 M NaCl) by equilibrium dialysis. Competition between Zn(II) and Co(II) for the first metal binding site suggests a value of 0.7 μM (pH 6.0, 30°C, 1 M NaCl) for the dissociation constant o Zn(II).The electronic spectra of the Co(II) enzyme lead to the suggestion that the coordination geometries around the metal ions in the first and second sites are related to those of a distorted tetrahedron and octahedron, respectively.     

Growth analysis of circular lichen thalli

A new model which describes the growth pattern of circular lichen thalli (foliose and placodioid) is developed. It is tested with published data and fits better than any previous models. A method is described for the calculation of the values of two constants, α and β which may be determined by the extent of lateral movement of carbohydrate and the rate of carbohydrate production respectively. It is believed that the model is sufficiently simple to be of general application in lichen ecology and physiology and in lichenometry.     

Effect of screening on the incidence of cervical cancer in Alberta.

The rates of registration of cases of in-situ and invasive cancer of the cervix in Alberta have fallen for women aged 35 and over since the introduction of screening in the early 1960s, as predicted by theory and described in Finland. However, for women aged 15 to 34 years of age the predicted pattern was followed only initially: the registration rate for in-situ and probably also invasive cancer increased after 1973. This could be due to an actual increase in the incidence of in-situ cancer of the cervix among younger women, as might be expected from the epidemiologic aspects of the disease, but it might also be due to increased recruitment of younger women to the screening program.     

Recent time-trends of age-specific death rates for breast cancer: Quebec and other provinces, 1965 through 1974.

For the 10-year period 1965 through 1974 the age-specific death rates for cancer of the breast decreased among middle-aged women, especially at ages 40 to 49 years, in Quebec, the Maritimes and the Prairies but not in Ontario or British Columbia. In women under 35 years of age the mortality generally increased, while in women aged 60 to 64 years there was little change except in the Prairies, where the rate increased. It seems probable that the trends reflect changes in incidence rather than in case-fatality. Some, but not all, of the pattern could be explained by changes in fertility over the past 50 years.     

Salmonellosis in gerbils induced by nonrelated experimental procedure.

An outbreak of salmonellosis in a gerbil colony was investigated. The clinical, bacteriologic, and pathologic findings are reported. Clinical signs included an occasional sudden death, depression, emaciation, dehydration, rough hair coat, and testicular enlargement. Not every sign was observed in every infected gerbil. At necropsy, 11 animals had lesions consistent with salmonellosis. Histopathologic lesions consisted of interstitial pneumonia, hepatic and splenic necrosis, meningitis, and suppurative orchitis. Splenic and intestinal amyloidosis were also noted. Salmonella, group D, was recovered from gerbil feces, a container in which adult mosquitos were reared, filarial inoculum, and a cockroach. An epizootiologic investigation led to salmonella-infected cockroaches as the possible source of animal contamination via mosquitos and the subsequent filarial inoculum.     

Experimental inoculation of raccoons (Procyon lotor) with rabies virus of skunk origin.

To determine raccoon (Procyon lotor) susceptibility and serum neutralizing antibody response to a skunk salivary gland rabies virus, raccoons were inoculated with a rabies virus isolated from a naturally-infected striped skunk (Mephitis mephitis). Raccoons were divided into four groups of three animals each. A dilution of the rabies virus suspension, 10(2.4), 10(3.4), or 10(4.8), mouse intracerebral lethal dose50 (MICLD50), was administered into the masseter muscles of each animal. Three negative control animals received only diluent. Saliva and sera were collected on post-inoculation days 35, 63 and 92 for virus isolation and determination of serum neutralizing antibody titer. All animals survived the 92 day observation period and none exhibited the behavioral changes classically associated with clinical rabies virus infections. Rabies virus was not detected in the saliva of any raccoon and two of the three animals receiving the highest inoculum developed serum neutralizing antibodies (SNA). On day 92, a challenge suspension of New York City/Georgia (NYC/GA) strain rabies virus in fox salivary glands (10(3.2) MICLD50) was administered to all 12 raccoons. All animals succumbed to rabies virus except the two animals that had earlier developed SNA. The results of this study provided evidence about the susceptibility of raccoons to a skunk rabies virus and demonstrated that exposed raccoons could survive for at least 92 days following exposure. Furthermore, animals developing SNA under such circumstances were capable of withstanding challenge with rabies virus that was fatal for seronegative raccoons.     

Steady-state head-to-tail polymerization of actin or microtubules. II. Two-state and three-state kinetic cycles

In a previous paper, bioenergetic aspects of head-to-tail polymerization for a two-state actin ATPase cycle were discussed. In section 2, here, the steady-state polymer length distribution for this case is derived. The distribution has the same mathematical form as at equilibrium, but the parameters are different. In section 3, both bioenergetic topics and the polymer length distribution are considered for the more general and realistic case of a three-state actin ATPase cycle. Again, the mathematical form of the steady-state distribution is the same as at equilibrium, but the parameters are more complicated. In section 4, the question is examined of how much the mean and variance of a polymer length distribution, obtained from a finite experimental sample of polymer (aggregate) molecules, would be expected to deviate from the true mean and variance (from an infinite sample). Also considered briefly in section 4 is the effect of hard polymer-polymer interactions on the equilibrium polymer length distribution, at finite polymer concentrations.