Differential responses of rabbit endocervix and uterus to medroxyprogesterone acetate

Uteri and cervices were obtained from estrous rabbits (controls) and from rabbits 24 h or 7 days after a single intramuscular injection of medroxyprogesterone acetate (MPA; 2.14 mg/kg). Estrogen and progesterone receptor concentrations were measured by Scatchard analysis, cell-free DNA synthesis was measured by (3H)-TTP incorporation, and tissue sections were examined histologically. The uterine endometrium underwent marked changes in histology, including extensive infoldings of the mucosal surface, glands were continuous into crypts and secretory epithelial cells were noted. In addition, total estrogen receptor content and DNA synthesis were decreased. In contrast, there was no significant change in the histology of the endocervical epithelial-stromal complex, and total estrogen receptor remained constant. However, DNA synthesis in the endocervix was decreased. Thus we conclude that: DNA synthesis is not linked to changes in estrogen receptor in the endocervix; and differential effects of progestogen on the estrogen receptor system occur coincident with different morphological responses within two target tissues from the same animal.     

The addition of CO2 to traditional taste solutions alters taste quality

Previous studies of the effect of carbonation on taste perception have suggested that it may be negligible, manifesting primarily in increases in the perceived intensity of weak salt and sour stimuli. Assuming CO2 solutions in the mouth stimulate only trigeminal nerve endings, this result is not altogether surprising; however, there are neurophysiological data indicating that CO2 stimulates gustatory as well as trigeminal fibers. In that case, carbonation might alter the quality profile of a stimulus without producing substantial changes in overall taste intensity--much as occurs when qualitatively different taste stimuli are mixed. To address this possibility, subjects were asked to rate the total taste intensity of moderate concentrations of stimuli representing each of the basic tastes and their binary combinations, with an without added carbonation. They then subdivided total taste intensity into the proportions of sweetness, saltiness, sourness, bitterness and 'other taste qualities' they perceived. The addition of carbonation produced only small increases in ratings of total taste intensity. However, rather dramatic alterations in the quality profiles of stimuli were observed, particularly for sweet and salty tastes. The nature of the interaction is consistent with a direct effect of carbonation/CO2 on the gustatory system, although the possibility that at least some of the observed effects reflect trigeminal-gustatory interactions cannot be ruled out.      

Environmental change, extinction and human activity: evidence from caves in NW Madagascar

In the last 2000 years, changes on the island of Madagascar have resulted in the modification of key environments and the extinction of nearly all large native animals. Humans have long been suspected as the primary cause of this ecological catastrophe, but the exact mechanisms of the island's rapid transformation and the role of natural factors such as climate change remain uncertain. Caves in northwestern Madagascar are helping researchers to disentangle these factors, by providing many types of datable information concerning the past in close physical proximity. U -series dated pollen spectra from the caverns of Anjohibe provide a 40,000-year record of vegetation in the vicinity. Bone deposits from caves in the region provide new site records for extinct taxa, including Babakotia radofilai Godfrey et al . 1990, Plesiorycteropus madagascariensis Filhol 1895, and Mullerornis sp. Several extant taxa that were present in the region in the late Holocene are now locally extinct. Archaeological evidence from the caves suggests little or no human activity in the vicinity or interaction with the fauna at these sites until recent centuries.     

A new ‘tapir’ from Ellesmere Island, Arctic Canada — Implications for northern high latitude palaeobiogeography and tapir palaeobiology

The oldest and northernmost record of the tapir lineage, Thuliadanta mayri gen. et sp. nov. from Ellesmere Island, Arctic Canada (78°50′N) implies that tapiroid evolution was well underway by early Eocene (Wasatchian) time in northern high latitudes, and raises the possibility of a North American origin for the group. Phylogenetic analyses place the new Arctic tapir as the sister group to the later more advanced Desmatotherium, Colodon, and Irdinolophus. A phylogenetically-derived biogeographic reconstruction posed here suggests the tapir lineage may represent a rare instance of counterflow wherein an exotic North American taxon invaded Asia during the early Eocene. Moreover, Thuliadanta seems a plausible ancestor to Desmatotherium from both continents, suggesting that this branch of the tapir lineage may have originated at high latitudes and subsequently dispersed from there to mid-latitudes. Thuliadanta's occurrence on Ellesmere Island indicates that northern high latitudes should also be evaluated as a potential source area for some of the exotic taxa appearing in mid-latitudes during Eocene time. Using today's tapirs, and specifically the mountain tapir, as analogs, Thuliadanta seems a plausible year-round inhabitant in the mild temperate lowland forests of the Eocene High Arctic.     

Extracellular iron reductase activity produced by Listeria monocytogenes

Little is known about how pathogenic microorganisms that do not produce low-molecular-weight iron-chelating agents, termed siderophores, acquire iron from their environment. We have identified an extracellular enzyme produced by Listeria monocytogenes that can mobilize iron from a variety of iron-chelate complexes via reduction of the metal. The iron reductase requires Mg²⁺, flavin mononucleotide (FMN), and reduced nicotinamide adenine dinucleotide (NADH) for activity. Saturation kinetics were found when initial velocity studies of iron reduction were carried out as a function of variable FMN concentrations in the presence of 100 μM NADH and 10 mM Mg²⁺. Hyperbolic kinetics were also found when these studies were repeated as a function of variable NADH concentrations along with 20 μM FMN and 10 mM Mg²⁺. This process of extracellular reduction, in all likelihood, could be involved in the mobilization of iron from soils and aqueous environments and from host tissues in pathogenic processes. This is the first report of the extracellular enzymic reduction of iron by microorganisms. Received: 12 March 1996 / Accepted: 16 April 1996     

Oral chemical irritation: does it reduce perceived taste intensity?

In an experiment in which capsaicin was presented in physicalmixture with taste stimuli, no reduction in perceived tasteintensity, relative to the control condition, was observed.This result is inconsistent with previous reports of taste intensityreductions when oral chemical irritants were only periodicallyinterspersed among taste stimuli (Lawless et al., 1985; Lawlessand Stevens, 1984). A second experiment directly compared thetwo presentation formats and their respective control conditionsin a repeated-measures design. The results of that test confirmthat greater apparent reductions in taste intensity are observedwhen the oral irritant is presented as a periodic rinse eventhough perceived irritation under rinse conditions regularlyfalls to levels significantly below those maintained with mixturepresentations. This observation indicates that much of the apparentmasking of taste intensity in the presence of oral irritationis not directly related to irritation level but is sensitiveto procedural variation.     

The role of iron in the production of hemolysin byListeria monocytogenes

The in vitro production of hemolysin byListeria monocytogenes, a facultative intracellular bacterial pathogen, was examined as a function of medium iron. There was an inverse relationship between iron and hemolysin production: Hemolysis increased as medium iron concentration decreased. This study offers the first evidence that the in vitro production of hemolysin byListeria monocytogenes is under the control of external iron in growth medium.