Hormonal factors and risk of aneurysmal subarachnoid hemorrhage - An international population-based, case-control study

Background and Purpose-Subarachnoid hemorrhage (SAH) is more common in women than in men, but the role of hormonal factors in its etiology remains uncertain. The aim of this study was to examine the relationship between hormonal factors and risk of SAH in women. Methods-This was a prospective, multicenter, population-based, case-control study performed in 4 major urban centers in Australia and New Zealand. Two hundred sixty-eight female cases of first-ever aneurysmal SAH occurred during 1995-1998. Controls were 286 frequency-matched women from the general population of each center. Outcome measures included risk of SAH associated with use of oral contraceptive pills (OCPs), hormone replacement therapy (HRT), and various endogenous hormonal factors including menstrual patterns, parity, age at birth of first child, and breast-feeding practices. Results-Cases and controls did not differ with regard to menstrual and reproductive history except in age at bir th of first child, where older age was associated with reduced risk of SAH (odds ratio [OR], 0.63; 95% CI, 0.43, 0.91). Relative to never use of HRT, the adjusted OR for over use of HRT was 0.64 (95% CI, 0.41, 0.98), which did not alter significantly after further adjustment for possible confounding factors. Borderline evidence of an inverse association was detected for past use of HRT (adjusted OR, 0.59; 95% CI, 0.30, 1.13) and current use of HRT (adjusted OR, 0.67; 95% CI, 0.40, 1.13), but there was no evidence of an association for use of OCPs (adjusted OR, 0.97; 95% CI, 0.58, 1.60). Conclusions-The risks of SAH are lower in women whose first pregnancy is at an older age and women who have ever used HRT but not OCPs. The findings suggest an independent etiologic role for hormonal factors in the pathogenesis of aneurysmal SAH and provide support for a protective role fur HRT on risk of SAH in postmenopausal women.

Spatial distribution of symbiotic shrimps (Periclimenes holthuisi, P-brevicarpalis, Thor amboinensis) on the sea anemone Stichodactyla haddoni

This study investigated the spatial distribution patterns of three shrimp species, Periclimenes holthuisi, P. brevicarpalis, and Thor amboinensis on the sea anemone Stichodactyla haddoni in the laboratory. Anemones were partitioned into five zones (mouth, inner tentacle, outer tentacle, upper column, and lower column), and shrimp distribution on these zones was determined. Regardless of species, significantly higher numbers of shrimps chose outer tentacles (>40%) over other zones during daytime. Such distribution might be attributed to their feeding practices as these crustaceans clipped and ate parts of the outer tentacles. Periclimenes holthuisi also showed varying temporal distribution patterns on their hosts. At night when anemones contracted their tentacles, shrimp moved in significant numbers from the outer tentacle region either to the column or off the anemones. Shrimps returned to the tentacles during daytime when anemones expanded their tentacles. Thus, spatial and temporal distribution of shrimps depend upon their feeding activities and degree of anemone expansion.

Feeding strategies for grain-fed cattle in a hot environment

Six Bos taurus (Hereford) steers (body weight 324 22 kg) were used in a 45-day study with a replicated 3 x 3 Latin-square design. Three treatments [ad libitum feeding (ADLIB); limit feeding, 85% of ad libitum (LIMIT); bunk management feeding where steers were only given access to feed from 1600 to 0800 hours the following day (BUNK)] were imposed over 3 periods, with 2 steers assigned to each treatment in each period. Cattle were managed in a temperature-controlled metabolism unit and were exposed to both thermoneutral (17.7degreesC-26.1degreesC) and hot (16.7degreesC-32.9degreesC) environmental conditions. By design, during the thermoneutral period, the ADLIB cattle displayed greater intake (P < 0.05) than the LIMIT group, with the BUNK group being intermediate. However, during the hot period, both the LIMIT and BUNK treatment groups increased feed intake 4-5%, whereas feed intake of the ADLIB treatment group declined nearly 2%. During both periods respiration rate (RR, breath/min) followed the same pattern that was observed for feed intake, with the greatest (P < 0.05) RR found in the ADLIB treatment group (81.09 and 109.55, thermoneutral and hot, respectively) and lowest (P < 0.05) RR in the LIMIT treatment group (74.47 and 102.76, thermoneutral and hot, respectively). Rectal temperature (RT) did not differ among treatments during the thermoneutral period or the first hot day, although during the thermoneutral period the ADLIB treatment group did tend to display a lower RT, possibly as a result of other physiological processes (pulse rate and RR) aiding to keep RT lower. During the hot period, differences in RT were found on Day 5, with the LIMIT cattle having lower (P < 0.10) RT (38.92degreesC) than the ADLIB (39.18degreesC) cattle, with BUNK cattle RT (39.14degreesC) being intermediate. However, when hourly data were examined, the ADLIB cattle had greater(P < 0.05) RT than the BUNK and LIMIT at 1800 hours and greater RT (P < 0.05) than the LIMIT group at 1400, 1500, and 1600 hours. Clearly, a change in diurnal RT pattern was obtained by using the LIMIT and BUNK feeding regimen. Both of these groups displayed a peak RT during the hot conditions, between 2100 and 2200 hours, whereas the ADLIB group displayed a peak RT between 1400 and 1500 hours, a time very close to when peak climatic stress occurs. Based on these results it is apparent that feedlot managers could alleviate the effects of adverse hot weather on cattle by utilising either a limit-feeding regimen or altering bunk management practices to prevent feed from being consumed several hours prior to the hottest portion of the day.

Anatomy of the mouthparts and digestive tract during feeding in larvae of the parasitoid wasp Trichogramma australicum Girault (Hymenoptera : Trichogrammatidae)

To aid in the development of artificial diets for mass rearing parasitioids, we investigated the anatomical changes in the digestive tract during feeding behaviour of larval Trichogramma australicum (Hymenoptera: Trichogrammatidae). Larvae begin to feed immediately upon eclosion and feed continuously for 4 h until replete. Feeding is characterised by rhythmic muscle contractions (ca 1 per s) of the pharynx. Contractions of the pharyngeal dilator muscles lift the roof of the lobe-shaped pharynx away from the floor of the chamber, opening the mouth and pumping food into the pharyngeal cavity. Another muscle contraction occurs about 0.5 s later, forcing the bolus of food through the oesophagus and into the midgut. The junction of fore- and midgut is marked by a cardiac valve. The midgut occupies most of the body cavity and is lined with highly vacuolated, flattened cells and a dispersed layer of muscle cells. In the centre of the midgut, food has the appearance of host egg contents. Food near the midgut epithelial cells has a finer, more homogeneous appearance. This change in the physical properties of the gut contents is indicative of the digestion process. In the prepupa, where digestion is complete, the entire gut contents have this appearance. After eclosion, the vitelline membrane remains attached to the posterior end of the larva. We believe this attachment to be adaptive in two ways: (1) to anchor the larva against the movements of its anterior portion, thereby increasing the efficiency of foraging within the egg, and (2) to prevent a free-floating membrane from clogging the mouthparts during ingestion. 1998 Elsevier Science Ltd. All rights reserved.

Observations on the diet and feeding habits of the epaulette shark, Hemiscyllium ocellatum (Bonnaterre), on Heron Island Reef, Great Barrier Reef, Australia

The diet and feeding habits of the epaulette shark, Hemiscyllium ocellatum, were investigated through stomach content analysis. Five groups of prey items were found. The index of relative importance showed worms and crabs,to be of greatest value at 51.3% and 40.1% respectively. The three minor prey groups were shrimps (7.7%), small fishes (0.7%) and amphipods (0.3%). Epaulette sharks tend to be crepuscular, although feeding bouts may occur at any time. They appear to be opportunistic predators, using olfaction and electroreception in prey capture. This species appears to be an important benthic predator in the reef flat environment on Heron Island Reef.

Grazers and diggers: Exploitation competition and coexistence among foragers with different feeding strategies on a single resource

A mathematical model is presented that describes a system where two consumer species compete exploitatively for a single renewable resource. The resource is distributed in a patchy but homogeneous environment; that is, all patches are intrinsically identical. The two consumer species are referred to as diggers and grazers, where diggers deplete the resource within a patch to lower densities than grazers. We show that the two distinct feeding strategies can produce a heterogeneous resource distribution that enables their coexistence. Coexistence requires that grazers must either move faster than diggers between patches or convert the resources to population growth much more efficiently than diggers. The model shows that the functional form of resource renewal within a patch is also important for coexistence. These results contrast with theory that considers exploitation competition for a single resource when the resource is assumed to be well mixed throughout the system.

Foraging and vein-cutting behaviour of Euploea core corinna (W.S. Macleay) (Lepidoptera : Nymphalidae) caterpillars feeding on latex-bearing leaves

Caterpillars of Euploea core corinna (W. S. Macleay) sever leaf veins prior to feeding on their latex-bearing host plants, which restricts the flow of latex at feeding sites. The severing of leaf veins by insects feeding on latex-bearing plants is commonly referred to as 'sabotaging' and is thought to be an evolved response by the insect to counter the negative effects of feeding on latex-rich leaves. Sabotaging behaviour is described for all instars of E. core corinna, with particular attention given to neonates. Vein cutting by neonate E. core corinna caterpillars can occur within 2 h of hatching, with most caterpillars establishing feeding sites within 10 h. Commonly, first instars cut an are-shaped row of leaf side-veins parallel to the leaf margin, but they may also cut the leaf mid-rib in a fashion similar to older instar larvae. From a sample of 50 E. core corinna larvae, representing all instars, we found that the diameters of the veins cut by caterpillars are closely correlated to larval head width (r=0.90). Through manipulative experiments, we demonstrate for the first time that sabotaging behaviour in neonate caterpillars imposes no detectable short-term physiological costs on those caterpillars.

A qualitative study of Australian GPs' attitudes and practices in the diagnosis and management of attention-deficit/hyperactivity disorder (ADHD)

Background. The importance of general practice involvement in the care of attention-deficit/hyperactivity disorder (ADHD) is increasing due to the rising numbers of patients who present with the disorder. It has been suggested by consensus bodies that GPs should be identifying and referring patients at the severe end of the ADHD spectrum and managing those with less severe symptoms. However, GPs' views of their role in ADHD care are unknown. Objective. Our aim was to explore the attitudes and practices of Australian GPs towards the diagnosis and management of ADHD. Methods. We conducted a series of focus groups to explore GPs' beliefs regarding the causes of ADHD, their perceived role in ADHD diagnosis and management and their views on the role of behaviour therapies and pharmacotherapies in ADHD management. The subjects were 28 GPs in six focus groups. Results. GPs in this study did not want to be the primary providers of care for patients with ADHD. Participants indicated a preference to refer the patient to medical specialists for diagnosis and treatment of ADHD, and expressed low levels of interest in becoming highly involved in ADHD care. Concerns about overdiagnosis and misdiagnosis of the disorder, diagnostic complexity, time constraints, insufficient education and training about the disorder, and concerns regarding misuse and diversion of stimulant medications were the reasons cited for their lack of willingness. Conclusions. The Australian GPs in this study identify a role for themselves in ADHD care which is largely supportive in nature, and involves close liaison with specialist services.