We describe a system for the expression of human coagulation factor IX in dog kidney cells in tissue culture, in which the post-translational modifications and the biochemical activity are indistinguishable from factor IX synthesized in vivo. This system has been used to express eight different point mutations of human factor IX in the first epidermal growth factor domain in order to study the role of F3-hydroxyaspartate at residue 64, and the adjacent carboxylate residues at positions 47, 49 and 78. We conclude that this domain is essential for factor IX function and suggest that Ca2+ binds to carboxylate ions in this domain and stabilizes a conformation necessary for the interaction of factor IXa with factor X, factor VIII and phospholipid in the next step of the clotting cascade.

Exposure to solar ultraviolet (UV) radiation is a known cause of skin cancer. Sunbed use represents an increasingly frequent source of artificial UV exposure in light‐skinned populations. To assess the available evidence of the association between sunbed use and cutaneous malignant melanoma (melanoma) and other skin cancers, a systematic review of the literature till March 2006 on epidemiological and biological studies on sunbed use was performed in Pubmed, ISI Web of Science, Embase, Pascal, Cochrane library, Lilacs and Medcarib. Search for keywords in the title and in the abstract was done systematically and supplemented by manual searches. Only case–control, cohort or cross‐sectional studies were selected. Data were abstracted by means of a standardized data‐collection protocol. Based on 19 informative studies, ever‐use of sunbeds was positively associated with melanoma (summary relative risk, 1.15; 95% CI, 1.00–1.31), although there was no consistent evidence of a dose–response relationship. First exposure to sunbeds before 35 years of age significantly increased the risk of melanoma, based on 7 informative studies (summary relative risk, 1.75; 95% CI, 1.35–2.26). The summary relative risk of 3 studies of squamous cell carcinoma showed an increased risk. For basal cell carcinoma, the studies did not support an association. The evidence does not support a protective effect of the use of sunbeds against damage to the skin from subsequent sun exposure. Young adults should be discouraged from using indoor tanning equipment and restricted access to sunbeds by minors should be strongly considered. © 2006 Wiley‐Liss, Inc.

The validity of the lithium clearance technique as a measure of end-proximal fluid delivery was assessed using micropuncture in sodium-replete, Inactin-anesthetized Sprague-Dawley rats. Three groups of animals were used: controls, amiloride treated, and furosemide treated. Diuretic-induced salt and water losses were replaced. Fractional lithium excretion (FELi) was 0.23 +/- 0.01, 0.24 +/- 0.02, and 0.40 +/- 0.03 in the control, amiloride, and furosemide groups, respectively. In each group, the tubular fluid-to-plasma lithium concentration ratio at the end of the proximal convoluted tubule (PCT) was significantly greater than unity (control, 1.16 +/- 0.03; amiloride, 1.16 +/- 0.02; furosemide, 1.17 +/- 0.02). In the control group, fractional lithium delivery (FDLi) at the late PCT was 0.50 +/- 0.02, while FDLi at the early distal tubule was 0.25 +/- 0.01; the latter did not differ significantly from FDLi at the late distal tubule or from FELi. Values in amiloride-treated rats were almost identical. Furosemide had no effect on FDLi at the late PCT, but raised that at the early distal tubule to 0.37 +/- 0.03. We conclude that 1) lithium reabsorption in the PCT lags slightly behind that of water, 2) substantial furosemide-sensitive lithium reabsorption occurs beyond the PCT, and 3) no significant lithium reabsorption occurs in nephron segments beyond the loop. These findings call into question the use of lithium clearance as a quantitative measure of end-proximal fluid delivery in sodium-replete animals.

Free-flow micropuncture was used to assess proximal and distal tubular function in rats immediately (2 to 5 hours), five days and 30 days after uninephrectomy (UN); results were compared with those in sham-operated littermates. Excretion rates of water, sodium and potassium were approximately doubled in the remaining kidney of UN rats. Two to five hours after UN there were small increases in glomerular filtration rate (GFR) and single nephron GFR which at this stage were not accompanied by an increase in absolute proximal reabsorption; that is, fractional proximal reabsorption fell. After five days, GFR and single nephron GFR had increased further; at this stage absolute proximal reabsorption was also significantly elevated. After 30 days, kidney weight, GFR, single nephron GFR and absolute proximal reabsorption had all increased by approximately 40%, and glomerulotubular balance in the proximal tubule had been fully restored. Data derived from distal tubular collections indicated that at every stage after UN: (a) fluid delivery to both early and late distal puncture sites was increased; (b) in contrast, there was no increase in sodium delivery to the late distal tubule, suggesting that the natriuresis resulted from reduced sodium reabsorption beyond the distal tubule and/or increased delivery of sodium from deep nephrons; and (c) there was a marked increase in potassium secretion into the accessible portion of the distal tubule which was more than adequate to explain the observed kaliuresis.

SUMMARY1. The possible pressor effect of vasopressin immediately after acute haemorrhage has been studied using anaesthetized Brattleboro rats with diabetes insipidus and rats of the Long Evans parent strain.2. A blood loss of 0.5 % of the body weight caused a significant decrease in mean arterial blood pressure, measured 10 min later, in Brattleboro rats, whereas this degree of haemorrhage was non-hypotensive in the control Long Evans rats.Following subsequent blood losses (each of 0-5 % of the body weight), mean arterial blood pressure in Brattleboro rats was always significantly lower than in Long Evans rats.3. While no antidiuretic activity was at any time found in the plasma of Brattleboro rats, haemorrhages greater than 1 % of the body weight were associated with marked increases in plasma arginine vasopressin (AVP) of Long Evans rats. 4. When Brattleboro and Long Evans rats were subjected to a single haemorrhage of 2 % of the body weight, the immediate decrease in arterial blood pressure was similar in the two groups. However, 5 and 10 min after the haemorrhage the arterial blood pressure was significantly higher in the Long Evans rats. When vasopressin was infused into Brattleboro rats so that plasma levels of the hormone approached those found in Long Evans rats, the mean arterial blood pressure 0, 5 and 10 min after haemorrhage was similar to that in the Long Evans animals. 5. It is concluded that in the anaesthetized rat, vasopressin plays an important role in the regulation of arterial blood pressure during the period immediately following acute haemorrhage.