The case for fencing remains intact.

Creel et al. argue against the conservation effectiveness of fencing based on a population measure that ignores the importance of top predators to ecosystem processes. Their statistical analyses consider, first, only a subset of fenced reserves and, second, an incomplete examination of 'costs per lion.' Our original conclusions remain unaltered.

Conserving large carnivores: dollars and fence.

Conservationists often advocate for landscape approaches to wildlife management while others argue for physical separation between protected species and human communities, but direct empirical comparisons of these alternatives are scarce. We relate African lion population densities and population trends to contrasting management practices across 42 sites in 11 countries. Lion populations in fenced reserves are significantly closer to their estimated carrying capacities than unfenced populations. Whereas fenced reserves can maintain lions at 80% of their potential densities on annual management budgets of $500 km(-2) , unfenced populations require budgets in excess of $2000 km(-2) to attain half their potential densities. Lions in fenced reserves are primarily limited by density dependence, but lions in unfenced reserves are highly sensitive to human population densities in surrounding communities, and unfenced populations are frequently subjected to density-independent factors. Nearly half the unfenced lion populations may decline to near extinction over the next 20-40 years.

Nucleus accumbens core lesions enhance two-way active avoidance.

The majority of work examining the nucleus accumbens core (NAc) has focused on functions pertaining to behaviors guided by appetitive outcomes. These studies have pointed to the NAc as being critical for motivating behavior toward desirable outcomes. For example, we have recently shown that lesions of the NAc impaired performance on a reward-guided decision-making task that required rats to choose between differently valued rewards. Unfortunately, much less is known about the role that the NAc plays in motivating behavior when aversive outcomes are predicted. To address this issue we asked if NAc lesions impact performance on a two-way active avoidance task in which rats must learn to shuttle back and forth in a behavioral training box in order to avoid a footshock predicted by an auditory tone. Although bilateral NAc lesions initially impaired reward-guided decision-making, we found that the same lesions improved acquisition and retention of two-way active avoidance.

Why do human cancer death rates increase with age? A new method of analysis of the biology of cancer.

1. Cancers, viewed as escape from the normal "contact inhibition" of cells in tissues, can be considered to start at some given time and then to require a period of incubation before they cause death. The probability of a start may depend on age, described by a start function. The incubation period may be described by a lethality function of the period between start and the age at which death rates are measured. 2. It can be shown that, provided the loss of tumour-bearers (where cancer has started) in the population by deaths from other causes than cancer is in the same ratio as the loss of total population, the differential curve (dR/dA) of the rate versus age curves must give the product of these two functions (start function X lethality function). 3. The differential curves dR/dA for major sites of cancers are examined for WHO data on deaths. The differential curves prove to be well described by normal Gaussian curves. The presence of more than one type of tumour or of physiological environment, included in a single category, is shown by multiple peaks in the differential curves. The outstanding exception is tumours of the "brain and other CNS" where the rate curve itself is Gaussian. 4. The results are consistent with a start rate that is random and independent of age (not exceeding three per 1,000 per year for the commonest tumour), and an astonishingly long incubation period of at least 20-50 years. For most sites, the curves indicate that from 20 to 40% of the cancers that have started do not cause death, because other causes supervene. 5. The implications as to the possibilities of control of cancer and of the relevance of experimental cancer research are discussed.

Direct measurement of potential difference across the human red blood cell membrane.

The electrical potential difference across the human red cell membrane has been measured directly. A biological amplifier with neutralized input capacity was used. Human red cells in modified Ringer solution were impaled individually with 3 M KCl-filled glass microelectrodes. Movements of the microelectrodes were effected by Leitz micromanipulators. Results showed a potential difference of -8.0 +/- 0.21 (SEM) mv, the inside being negative with respect to the outside. This value is approximately that calculated by using the Nernst equation considering the intracellular and extracellular chloride concentrations.As a control, similar measurements were made on nylon microcapsules containing hemoglobin. The measured potential of -0.52 +/- 0.02 (SEM) mv, which agreed very well with the value calculated on the basis of Donnan equilibrium, was much smaller in magnitude as compared to the results for the red cell, and there was evidence of fixed charges on the microcapsule membrane. There was no evidence of this in the case of the red cell.

The relation of cycling of intracellular pH to mitosis in the acellular slime mould Physarum polycephalum.

The relation between intracellular pH and the mitotic cycle of Physarum polycephalum was studied by two-independent techniques. Both techniques revealed a long term cycling of intracellular pH which has the same period as the mitotic cycle, Qualitative detection of the changes in intracellular pH was made by measuring the changes in fluorescence of 4-methylesculetin which had been absorbed by the plasmodium. Quantitative measurements of intracellular pH were made throughout the mitotic cycle with antimony micro pH electrodes. The cycle of intracellular pH is sinusoidal in appearance. The maximum intracellular pH (pH 6.6) occurred at, or very near to, mitosis, and was approximately 0.6 pH units higher than the minimum pH, which occurred near the middle of the mitotic cycle.

Pelvic actinomycosis associated with IUCD.

PIP: Tuboovarian actinomycosis may be more commonly associated with a plastic IUD than has been thought. Serological tests for actinomycosis may be useful in the diagnosis and management of this infection. In a case in which ovarian biopsy at laparotomy revealed typical actinomycotic "sulphur granules" and Actinomyces israelii was diagnosed, standard Actinomyces israelii cytoplasmic antigens and circulating C1-binding immune complexes were found in the patient's serum when it was tested by counterimmunoelectrophoresis. This organism had not been isolated through oral and cervical cultures, thus serology could provide an otherwise missed diagnosis. The diappearance of the circulating immune complexes could indicate adequacy of treatment.^ieng