Burnout was strongly related to alcohol abuse/dependence among sampled medical students and increased educational debt predicted a higher risk. A multifaceted approach addressing burnout, medical education costs, and alcohol use is needed.

The teats of 18 cows were externally exposed to infection with mastitis organisms by dipping them daily for 1 or 2 weeks in a mixed suspension of Streptococcus dysgalactiae and Str. uberis at the start, the middle or the end of the dry period. The teat sinuses of quarters which remained uninfected after external exposure at the beginning or the middle of the dry period were then infused with the same strains of streptococci. Of the 9 quarters infected following external exposure 8 occurred in animals exposed at the start and one in the middle of the dry period. Thirty-six new infections occurred after infusion of bacteria into the teat sinuses of 38 quarters. In a further trial with 10 cows, Staphylococcus aureus and Str. zooepidemicus were inoculated into the distal 3 mm of the streak canals of 5 cows immediately after drying-off and into those of 5 cows which had been dry for 28 weeks. Animals were slaughtered 48 h later and infection determined by teat puncture. Five infections occurred in cows which were at the start of the dry period and only one in the cows dry for 28 weeks. It is suggested that these differences in the rates of new infection between the early dry period and a very extended dry period are due to differences in the ease with which bacteria can penetrate the teat canal. At the later stage bacterial growth through the teat canal appeared to be inhibited.The unmilked udder is particularly susceptible to infection in the 3 weeks following drying-off (Neave, Dodd & Henriques, 1950). Indeed, rates of new infection during the dry period exceed those of lactation, which may be due to the absence of the flushing out effect of regular milking (Neave et al. 1968; Thomas etal. 1972). However, this could not account for the large difference in the rate of new infection between the early part and the later part of the dry period. This difference may be due to the higher level of exposure to bacteria at the beginning of the dry period, i.e. bacteria remaining on the teat skin from the preceding lactation period. Alternatively, progressive changes in the composition of the udder secretion during the dry period (Wheelock et al. 1967;Smith, Wheelock & Dodd, 19676) may influence the establishment of infection after bacterial penetration of the streak canal. It is also possible that changes within the streak canal, such as the formation of a natural seal, may make bacterial penetration more difficult in later stages of the dry period. The aim of the experiments described in this paper was to investigate further the changes in susceptibility to new infection during the dry period. Two experiments were carried out; the first was designed to expose the udders of dairy cows to similar numbers of pathogenic bacteria either at the beginning, the middle or towards the end of the dry period and to measure the resulting numbers of new infections. The second

Nicotine causes dose-dependent alterations in accuracy on the differential-reinforcement of low-rate responding (DRL) 29.5-s schedule in rats. The current investigation evaluated whether nicotineassociated contextual cues can produce nicotine-like perturbations in DRL-schedule performance in the absence of nicotine. Nicotine and saline administrations occurred just prior to DRL 29.5-s schedule responding for sucrose solution, and two different experimental contexts (differentiated by visual, olfactory, and tactile cues) were utilized. All subjects (N = 16) experienced two consecutive daily sessions of DRL-schedule responding per day. The experimental group (n = 8) was exposed to saline immediately prior to the first session and 0.3mg/kg nicotine before the second session, and the context was changed between sessions. This sequence of saline and then nicotine administration, paired with two reliable contexts, persisted for 12 consecutive days and successive nicotine administrations corresponded with increasingly poorer performance on the DRL 29.5-s schedule. No nicotine was administered for days 13-20 during context testing, and the nicotine-associated context produced response disinhibition on the DRL schedule. Two control groups were included in the design; subjects in one control group (n = 4) received saline in each context to verify that the contexts themselves were not exerting control over operant responding. To assess how explicit and nonexplicit pairings of nicotine and contextual cues influenced DRL behavior, subjects in a second control group (n = 4) were given nicotine prior to the second session, but the contexts were not altered between sessions. The results from this experiment suggest that environmental stimuli associated with nicotine exposure can come to elicit nicotine-induced performance decrements on a DRL 29.5-s schedule.

A within herd comparison of teat dipping and dry cow therapy (full treatment) with only selective dry cow therapy (partial treatment) was carried out in six commercial dairy herds for a two year period. In four herds, the incidence of clinical mastitis was 2 to 12 per cent higher in the partial treatment group. In another herd, in which the pattern of clinical mastitis isolates was unusual in that minor pathogens were isolated from 30 per cent of mastitis cases, the incidence was 43 per cent higher in the partial treatment group. In the remaining herd the incidence was 10 percent higher in the full treatment group. Streptococcus uberis mastitis was more common in the partial treatment groups of five herds; coliform mastitis was more common in the full treatment groups of two herds and similar in both groups in the other herds. High rates of coliform mastitis were associated with poor herd environmental conditions but this was not true for Strep uberis mastitis. Rates of staphylococcus aureus and Strep dysgalactiae mastitis were low in all herds. The level of major pathogen infection in cows completing the trial in all herds increased in the partial treatment group from 5 per cent of quarters at the start to 12 per cent at the finish of the trial. In the full treatment group, however, there was only a small increase in this level. In contrast, levels of Corynebacterium bovis infection increased by 17 per cent in both treatment groups. Continued use of teat dipping and dry cow therapy was associated with a higher rate of coliform mastitis in two of the three herds where there were poor standards of hygiene and husbandry.

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A conjunctive variable-interval differential-reinforcement-of-low-rate (VI-DRL, n= 18) responding schedule and a stop-signal task (n= 18) were used to evaluate the disinhibiting effects of nicotine on response withholding in rats. Sucrose solution was used to reinforce responding, and after a stable baseline was achieved under saline-administration conditions, 0.3 mg/kg nicotine was delivered before each session. Experiment 1 showed that repeated, but not the initial, administration of nicotine decreased performance on both tasks, and the effect of sensitization followed a similar timeline; 10 consecutive doses resulted in poorer proportion-correct VI-DRL trials and percent correct stop trials than the initial dose of nicotine. Furthermore, sensitization to 0.3 mg/kg nicotine decreased performance regardless of whether a spaced or consecutive-dosing regimen was followed. Experiment 2 was designed to test whether mecamylamine hydrochloride (0.1–1.0 mg/kg) could attenuate the effects of repeated 0.3 mg/kg nicotine administration, and the degree to which mecamylamine attenuation of the effect of nicotine to produce impulsive action was relative to dose. Results from experiment 2 showed that response disinhibition, as evaluated using the VI-DRL and stop-signal tasks, is related in a systematic manner to nicotinic-acetylcholine receptor activation.

Objective To assess whether asthma is associated with risk of appendicitis in children. Methods We used a population-based case-control study design utilizing a comprehensive medical record review and predetermined criteria for appendicitis and asthma. All children (age<18 years) who resided in Olmsted County, Minnesota, and developed appendicitis between 2006 and 2012 were matched to controls (1:1) with regard to birthday, gender, registration date, and index date. Asthma status was ascertained using predetermined criteria. Active (current) asthma was defined as the presence of asthma symptoms or asthma-related events (eg, medication use, clinic visits, emergency department, or hospitalization) within one year prior to the index date. Inactive asthma was defined as subjects without these events. A conditional logistic regression model was used. Results Among the 309 appendicitis cases identified, when stratified by asthma status, active asthma was associated with significantly increased risk of appendicitis when compared to inactive asthma (OR=2.48; 95% CI, 1.22–5.03) and to no asthma (OR=1.88; 95% CI, 1.07–3.27) (overall p-value=0.035). When controlling for potential confounders such as gender, age, and smoking status, active asthma was associated with a higher odds of developing appendicitis compared to non-asthmatics (adjusted OR=1.75, 95% CI 0.99–3.11) whereas inactive asthma was not (overall p-value=0.049). Tobacco smoke exposure within three months was associated with an increased risk of appendicitis (adjusted OR=1.66; 95% CI, 1.02, 2.69). Among asthma medications, leukotriene receptor antagonists reduced the risk of appendicitis (OR=0.18; 95% CI, 0.04–0.74). Conclusions Active asthma may be an unrecognized risk factor for appendicitis in children while a history of inactive asthma does not pose such risk. Further investigation exploring the underlying mechanisms is warranted.

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