Leith C. R. Meyer

A Review of Current Intravaginal Drug Delivery Approaches Employed for the Prophylaxis of HIV/AIDS and Prevention of Sexually Transmitted Infections

The objective of this review is to describe the current status of several intravaginal anti-HIV microbicidal delivery systems these delivery systems and microbicidal compounds in the context of their stage within clinical trials and their potential cervicovaginal defence successes. The global Human Immuno-Deficiency Virus (HIV) pandemic continues to spread at a rate of more than 15,000 new infections daily and sexually transmitted infections (STIs) can predispose people to acquiring HIV infection. Male-to-female transmission is eight times more likely to occur than female-to-male transmission due to the anatomical structure of the vagina as well as socio-economic factors and the disempowerment of women that renders them unable to refuse unsafe sexual practices in some communities. The increased incidence of HIV in women has identified the urgent need for efficacious and safe intravaginal delivery of anti-HIV agents that can be used and controlled by women. To meet this challenge, several intravaginal anti-HIV microbicidal delivery systems are in the process of been developed. The outcomes of three main categories are discussed in this review: namely, dual-function polymeric systems, non-polymeric systems and nanotechnology-based systems. These delivery systems include formulations that modify the genital environment (e.g. polyacrylic acid gels and lactobacillus gels), surfactants (e.g. sodium lauryl sulfate), polyanionic therapeutic polymers (e.g. carageenan and carbomer/lactic acid gels), proteins (e.g. cyanovirin-N, monoclonal antibodies and thromspondin-1 peptides), protease inhibitors and other molecules (e.g. dendrimer based-gels and the molecular condom). Intravaginal microbicide delivery systems are providing a new option for preventing the transmission of STIs and HIV.

Body temperature, thermoregulatory behaviour and pelt characteristics of three colour morphs of springbok (Antidorcas marsupialis).

Using intra-abdominal miniature data loggers, we measured core body temperature in female springbok (Antidorcas marsupialis) of three colour morphs (black, normal and white), free-living in the Karoo, South Africa, for one year. During winter, white springbok displayed lower daily minimum body temperatures (37.4+/-0.5 degrees C), than both black (38.1+/-0.3 degrees C) and normal (38.0+/-0.6 degrees C) springbok. During spring, black springbok displayed higher daily maximum body temperatures (40.7+/-0.1 degrees C) than both white (40.2+/-0.2 degrees C) and normal (40.2+/-0.2 degrees C) springbok. These high maximum body temperatures were associated with larger daily amplitudes of nychthemeral rhythm of body temperature (2.0+/-0.2 degrees C), than that of white (1.6+/-0.1 degrees C) and normal (1.7+/-0.2 degrees C) springbok. Biophysical properties of sample springbok pelts were consistent with these patterns, as the black springbok pelt showed lower reflectance in the visible spectral range, and higher heat load from simulated solar radiation, than did the pelts of the other two springbok. Black springbok had lower diurnal activity in winter, consistent with them having to forage less because their metabolic cost of homeothermy was lower, but were disadvantaged in hot periods. White springbok, by contrast, were more protected from solar heat load, but potentially less able to meet the energy cost of homeothermy in winter. Thus energy considerations may underlie the rarity of the springbok colour morphs.

HYPERTHERMIA IN CAPTURED IMPALA (AEPYCEROS MELAMPUS): A FRIGHT NOT FLIGHT RESPONSE

To investigate the patterns and mechanisms of capture-induced hyperthermia, we surgically implanted 26 impala (Aepyceros melampus) with miniature thermometric data loggers, which measured body temperatures continuously throughout capture procedures. Four groups of impala, which were habituated to varying levels of handling and boma-housing, were captured by net restraint or by chemical immobilization. The study took place between July 1999 and December 2005. Irrespective of whether impala were chemically captured, net-captured, or disturbed by exposure to a stressor, they developed a precipitous increase in body temperature. This increase in body temperature was not related to activity levels; animals that had low activity levels before immobilization had larger increases in body temperature compared to those that had high activity levels but were not immobilized (t=3.6, P=0.001, n=5). Similarly this increase in body temperature was not related to environmental heat load at the time of darting and immobilization (r=−0.05, P=0.85). Body temperature increase also did not depend on whether the animals were captured using drugs or not. However, we found that those animals that were habituated more to handling and boma-housing had smaller increases in body temperatures (F=37, P<0.001) and smaller stress responses, indicated by lower plasma cortisol concentrations (F=5.5, P<0.05), and less fractious behavior, compared to those animals that were habituated less or not at all. Therefore we believe that capture-induced hyperthermia in impala is caused predominantly by stress, which induces a rapid rise in body temperature.

Ostriches sleep like platypuses.

Mammals and birds engage in two distinct states of sleep, slow wave sleep (SWS) and rapid eye movement (REM) sleep. SWS is characterized by slow, high amplitude brain waves, while REM sleep is characterized by fast, low amplitude waves, known as activation, occurring with rapid eye movements and reduced muscle tone. However, monotremes (platypuses and echidnas), the most basal (or ‘ancient’) group of living mammals, show only a single sleep state that combines elements of SWS and REM sleep, suggesting that these states became temporally segregated in the common ancestor to marsupial and eutherian mammals. Whether sleep in basal birds resembles that of monotremes or other mammals and birds is unknown. Here, we provide the first description of brain activity during sleep in ostriches (Struthio camelus), a member of the most basal group of living birds. We found that the brain activity of sleeping ostriches is unique. Episodes of REM sleep were delineated by rapid eye movements, reduced muscle tone, and head movements, similar to those observed in other birds and mammals engaged in REM sleep; however, during REM sleep in ostriches, forebrain activity would flip between REM sleep-like activation and SWS-like slow waves, the latter reminiscent of sleep in the platypus. Moreover, the amount of REM sleep in ostriches is greater than in any other bird, just as in platypuses, which have more REM sleep than other mammals. These findings reveal a recurring sequence of steps in the evolution of sleep in which SWS and REM sleep arose from a single heterogeneous state that became temporally segregated into two distinct states. This common trajectory suggests that forebrain activation during REM sleep is an evolutionarily new feature, presumably involved in performing new sleep functions not found in more basal animals.

Activity re-assignment and microclimate selection of free-living Arabian oryx: responses that could minimise the effects of climate change on homeostasis?

Predicting whether behaviour could buffer the effects of climate change on long-lived mammals requires a better understanding of the long-term behavioural responses of mammals to environmental stress. Using biologging, we measured locomotor activity and microclimate selection, over eight months, in five Arabian oryx (Oryx leucoryx) living free in a Saudi Arabian desert. The oryx displayed seasonal flexibility in activity patterns, shifting from a continuous 24-h activity pattern with crepuscular peaks in cooler months to a predominantly nocturnal activity pattern during the hottest months, without reducing the total 24-h activity level. The proportion of total 24-h activity that occurred during daylight hours was just 29±8% during the hottest months, versus 53±8% (mean±SD, n=5 oryx) in the other months. The attenuation in diurnal activity levels during the hot months was accompanied by the selection of cooler microclimates, presumably via shade seeking, during the heat of the day. Analysis of miniature black globe (miniglobe) temperature from a remote sensor on the collar of two female animals revealed that oryx selected microclimates cooler than the microclimates in direct sun at higher environmental heat loads across all periods, but with enhanced efficiency during the dry periods. We have quantified activity re-assignment and microclimate selection as responses to hot arid conditions in a free-living artiodactyl. Such flexible behavioural processes may act to buffer the adverse effects of the progressively hotter and drier conditions predicted to occur with climate change.

Minimum daily core body temperature in western grey kangaroos decreases as summer advances: a seasonal pattern, or a direct response to water, heat or energy supply?

SUMMARY Using implanted temperature loggers, we measured core body temperature in nine western grey kangaroos every 5 min for 24 to 98 days in spring and summer. Body temperature was highest at night and decreased rapidly early in the morning, reaching a nadir at 10:00 h, after ambient temperature and solar radiation had begun to increase. On hotter days, the minimum morning body temperature was lower than on cooler days, decreasing from a mean of 36.2°C in the spring to 34.0°C in the summer. This effect correlated better with the time of the year than with proximate thermal stressors, suggesting that either season itself or some factor correlated with season, such as food availability, caused the change. Water saving has been proposed as a selective advantage of heterothermy in other large mammals, but in kangaroos the water savings would have been small and not required in a reserve with permanent standing water. We calculate that the lower core temperature could provide energy savings of nearly 7%. It is likely that the heterothermy that we observed on hot days results either from decreased energy intake during the dry season or from a seasonal pattern entrained in the kangaroos that presumably has been selected for because of decreased energy availability during the dry season.

Cheetah do not abandon hunts because they overheat

Hunting cheetah reportedly store metabolic heat during the chase and abandon chases because they overheat. Using biologging to remotely measure the body temperature (every minute) and locomotor activity (every 5 min) of four free-living cheetah, hunting spontaneously, we found that cheetah abandoned hunts, but not because they overheated. Body temperature averaged 38.4°C when the chase was terminated. Storage of metabolic heat did not compromise hunts. The increase in body temperature following a successful hunt was double that of an unsuccessful hunt (1.3°C ± 0.2°C versus 0.5°C ± 0.1°C), even though the level of activity during the hunts was similar. We propose that the increase in body temperature following a successful hunt is a stress hyperthermia, rather than an exercise-induced hyperthermia.

EFFECTS OF SEROTONIN AGONISTS AND DOXAPRAM ON RESPIRATORY DEPRESSION AND HYPOXEMIA IN ETORPHINE-IMMOBILIZED IMPALA (AEPYCEROS MELAMPUS)

Respiratory depression is a common side effect when opioids are used to immobilize wildlife. Serotonergic ligands have the potential to reverse opioid-induced respiratory depression. We examined whether any of three serotonergic ligands could reverse this depression in etorphine-immobilized (0.07 mg/kg) impala (Aepyceros melampus). The study took place in September–December 2007. Impala received intravenous injections of metoclopramide (10 mg/ kg, n=6), buspirone (0.05 mg/kg, n=8), pimozide (1 mg/kg, n=8), doxapram (1 mg/kg, n=6), and control solutions on separate occasions. During the immobilization, partial pressures of oxygen (PaO2, mmHg) and carbon dioxide (PaCO2, mmHg), respiratory rate (breaths/min), ventilation (l/ min), peripheral O2 saturation (%), tidal volume (l), and respiratory exchange ratio were measured before and after injection of the experimental drugs. Etorphine immobilization caused respiratory depression and hypoxia (mean±SD, PaCO2=51±2 mmHg, PaO2=40±3 mmHg). Metoclopra-mide and buspirone, but not pimozide, attenuated the hypoxic effects of etorphine; 3 min after injection, metoclopramide increased the PaO2 by 7.=66.3 mmHg and buspirone by 666.6 mmHg (F=3.9, P=0.02). These effects were similar to those of doxapram (8±7 mmHg, F=3.9; P>0.05). Neither metoclopramide nor buspirone significantly increased ventilation, but they increased PaO2 by significantly improving the alveolar-arterial oxygen partial pressure gradient (A-a gradient, F=1.4, P<0.05), indicating improved oxygen diffusion. Metoclopramide and buspirone transiently improved blood oxygenation of opioid-immobilized impala, probably by improving ventilation-perfusion ratios, without reversing catatonic immobilization.

In vitro and ex vivo bioadhesivity analysis of polymeric intravaginal caplets using physicomechanics and computational structural modeling.

The in vitro and ex vivo bioadhesivity of polyacrylic acid (PAA)-based intravaginal caplets was explored from a physicomechanical and chemometrical structural modeling viewpoint. An Extreme Vertices Mixture Design was constructed for analyzing the bioadhesivity of 11 matrices that were optimized. Two sets of crosslinked PAA-based matrices comprising either allyl-sucrose (AS-PAA) or allyl-penta-erythritol (APE-PAA) were explored. Powders were compressed into caplet-shaped matrices and rotational rheological analysis was performed on hydrated polymeric blends. Caplets were evaluated for bioadhesiveness using a simulated vaginal membrane (SVM) with optimized caplets further tested using freshly excised rabbit vaginal tissue. The SVM and caplets were hydrated in simulated vaginal fluid before bioadhesivity testing using a texture analyzer to determine the rupture force between the membranous substrates and hydrated caplets. Computational and molecular structural modeling deduced transient sol-gel mechanisms, chemical interactions and inter-polymeric interfacing during caplet-substrate bioadhesion. Peak adhesive force (PAF) and work of adhesion (AUC(FD)) values for the APE-PAA caplets (1.671+/-0.232N; 0.0010+/-0.0002J) were higher than the AS-PAA caplets (1.168+/-0.093N; 0.00030+/-0.0001J) revealing superior bioadhesiveness. Similarly, rheological analysis revealed APE-PAA blends with higher viscosity and shear stress values (9x10(5)mPa/180Pa). The optimized APE-PAA matrices adhered appreciably to rabbit vaginal tissue (PAF=0.883+/-0.083N; AUC(FD)=(0.0003+/-3.5355)x10(-5)J). Results strongly suggest that the approach may be useful for assessing the bioadhesivity of intravaginal matrices on ex vivo rabbit vaginal tissue with data further supported by molecular structural analysis and energy-dependant bioadhesivity modeling.

Energy intake and the circadian rhythm of core body temperature in sheep

We tested the hypothesis that different levels of energy intake would alter the circadian rhythm of core body temperature (Tc) in ovariectomized sheep. We measured arterial blood temperature every 5 min while ten sheep were offered a maintenance diet, 70% of maintenance requirements, or 150% of maintenance requirements, for 12 days, and later fasted for 2 days. The rhythmicity of Tc was analyzed for its dominant period and then a least‐squares cosine wave was fitted to the data that generated a mesor, amplitude, and acrophase for the rhythm. When energy intake was less than maintenance requirements we observed a significant decrease in the mesor and minimum, and a significant increase in the amplitude and goodness of fit, of the body temperature rhythm. Fasting also resulted in a decrease in the maximum of the body temperature rhythm. Feeding the sheep to excess did not affect the mesor or maximum of the rhythm, but did result in a decrease in the goodness of fit of the rhythm in those sheep that consumed more energy than when they were on the maintenance diet, indicating that circadian rhythmicity was decreased when energy intake increased. Our data indicate that modulation of the circadian rhythm of body temperature, characterized by inactive‐phase hypothermia, occurs when energy intake is reduced. The response may be an adaptation to energy imbalance in large mammals.