Involvement of prolactin in the REM sleep-promoting activity of systemic vasoactive intestinal peptide (VIP)

The involvement of pituitary prolactin (PRL) in systemic vasoactive intestinal peptide (VIP)-induced sleep was studied. Male rats were implanted with electrodes for EEG-recording, with brain thermistors to record cortical temperature (T_crt) and with chronic intracardial catheters to obtain blood samples and to deliver substances. One group of rats (n = 8) received normal rabbit serum (NS) + physiological saline (SAL) on the baseline day and was injected with NS + VIP on the experimental day. In the other group of rats (n = 6), the baseline day was followed by administration of PRL-antiserum (PRL-AS) + VIP on the experimental day. The sera and VIP or SAL were injected 30 min before and at light onset, respectively. Sleep-wake activity was then recorded for the next 12-h light period. Systemic VIP-stimulated PRL secretion as measured by RIA in serial samples obtained hour 1 postinjection. VIP also elicited selective increases in REM sleep (REMS) in the rats pretreated with NS. T_crt was not affected by VIP. Administration of PRL-AS blocked the increase in circulating levels of free (non-IgG-bound) PRL and prevented VIP-enhanced REMS. Comparisons of the sleep effects of PRL-AS + VIP with the previously reported changes in sleep after PRL-AS alone indicate that PRL has a major role in the mediation of the REMS-promoting activity of systemic VIP. The results suggest that an increased release of endogenous pituitary PRL modulates REMS.     

Increase of prolactin mRNA in the rat hypothalamus after intracerebroventricular injection of VIP or PACAP

Vasoactive intestinal peptide (VIP), the structurally homologous pituitary adenylate cyclase-activating peptide (PACAP) and the pituitary hormone, prolactin (PRL) enhance rapid eye movement sleep (REMS). VIP and PACAP are both inducers of PRL gene expression and release in the pituitary gland. Little is known about PRL regulation in the brain although it is hypothesized that the REMS-promoting activity of i.c.v. administered VIP may be mediated via the activation of cerebral PRL. To test whether VIP or PACAP in fact increase intracerebral mRNA, the peptides (VIP: 30 or 300 pmol; PACAP: 220 pmol) were injected i.c.v. into rats at dark onset. 1 h later, cDNA was synthesized from purified hypothalamic mRNA. Standardized amounts were analysed for PRL using the polymerase chain reaction followed by Southern blotting and hybridization. Compared with β-actin mRNA levels, both VIP and PACAP increased PRL mRNA levels in a dose-dependent fashion though VIP was more effective on a molar basis. The previously reported alternatively spliced PRL mRNA (lacking exon 4) was not detected. The data support the hypothesis that the REMS-promoting activity of central VIP and PACAP might be mediated by cerebral PRL.     

Risk factors for neck pain in office workers: a prospective study

Background  

Persisting neck pain is common in society. It has been reported that the prevalence of neck pain in office workers is much higher than in the general population. The costs to the worker, employer and society associated with work-related neck pain are known to be considerable and are escalating. The factors that place office workers at greater risk of developing neck pain are not understood. The aim of this study is to investigate the incidence and risk factors of work-related neck pain in Australian office workers.     

Managing recurrent urinary catheter blockage: problems, promises, and practicalities.

Long-term urinary catheterization is rarely completely free of complications, and encrustation by mineral salts leading to catheter blockage is common in around 40% to 50% of long-term catheterized patients. Recurrent blockage is a problem, which is both distressing to patients and caregivers and costly to health services in terms of time and resources. This article addresses the causes of recurrent urinary catheter blockage, proactive approaches to care, and the evidence for use of catheter maintenance solutions to reduce buildup of mineral deposits.     

Problems measuring contrast sensitivity in children

A preliminary study measured the contrast sensitivity function (CSF) in 30 children (aged 3 months-5 years). Preferential looking techniques were used to assess CSF to sine wave gratings displayed on one of two screens. To find a meaningful contrast sensitivity procedure we compared the results with a shorter procedure using an edge stimulus. The following problems were encountered: measuring the contrasts required to detect four or five different spatial frequencies took time, resulting in boredom and loss of attention in our subjects; there was poor correlation between CSF and edge detection; an interesting artefact resulted in a plateau rather than a low frequency fall-off in the CSF of five of the children greater than 30 months old. This artefact may have resulted from peripheral rather than central retinal responses and/or motion artefacts in the stimulus onset. A follow up study with 41 additional children aged 3-36 months limited the contrast testing to that of the spatial frequency corresponding to the peak of the CSF. The shortened procedure, plus a lot of encouragement, resulted in higher contrast sensitivities in all but the oldest age group and successful monocular contrast measurements. In order to avoid artefacts arising from peripheral vision, children were encouraged to look at each screen before responding.