Neonatal and adult rabbit renal brush border membrane vesicle solute reflection coefficients

The interaction between solute and water in epithelial transport is represented by the solute reflection coefficient. Because the osmotic water transport process changes in the rabbit proximal tubule during maturation, there is a potential for the solute reflection coefficients to also undergo maturational changes. In the present study, we directly examined solute reflection coefficients in neonatal and adult brush border membrane vesicles (BBMV) using the stop-flow light-scattering technique. Reflection coefficients for NaCl, KCl, NaHCO3 and urea were found to be identical in the neonatal and adult BBMV and were not different from 1. Thus, although the water transport pathway undergoes changes in the proximal tubule during maturation, there is no evidence for changes in solute and water interaction. Because the reflection coefficients are not different from 1, there is no evidence for solvent drag in the proximal tubule apical membrane in either the neonatal or adult tubule.

Increased training load and the beta-adrenergic-receptor system on human lymphocytes

The influence of increased training on the sympathoadrenergic system was investigated. Moderately trained male subjects (n = 15) increased their training within 10 wk by 60%; eight of the subjects increased their training volume, and seven increased their training intensity. Before and after the training, an exhaustive treadmill exercise was carried out. Acute treadmill exercise increased beta-adrenergic receptor number on mononuclear lymphocytes, isoproternol-stimulated cAMP production, and plasma catecholamine concentration. The increase of receptor number can at least partially be explained by a changed lymphocyte composition at rest and after exercise. After training, the exercise-induced increase of beta-adrenergic receptor number was significantly blunted, and the exercise-induced increase of the isoproternol-stimulated cAMP production per beta-receptor was enhanced. Subjects who experienced increased symptoms of physical discomfort and/or mood changes showed an enhanced cAMP production after training. These findings point to an altered regulation of the receptor and postreceptor mechanisms as an effect of a 10-wk period of hard training.

Drug use and syphilis. Co-factors for HIV transmission among commercial sex workers in Guyana

A cross-sectional survey was conducted among 124 street- and brothel-based female commercial sex workers (CSWs) in Georgetown in January and February 1997 to determine the seroprevalence of human immunodeficiency virus (HIV) infection and describe the sexual practices and drug use patterns. Their median age was 30 years (range 17 to 52 years). 119 (88%) reported regular alcohol consumption while looking for clients, 27 (22%) said they smoked cocaine and 51 (42%) reported use of marijuana. Street-based CSWs were significantly more likely to report marijuana use (p = 0.033). 72% reported that they never used condoms with regular sex partners and 35% reported that they never used condoms with clients. Brothel-based women were significantly more likely to report consistent condom use with their clients (p = 0.05). 46% (54/118) tested HIV positive and 28% (33/118) had a positive serological test for syphilis. Factors that were significantly associated with HIV infection included a positive serological test for syphilis (OR = 7.56; 95% CI = 2.7-21.97; p < 0.01) and a history of having received treatment for syphilis (OR = 2.93; 95% CI = 1.12-7.8). Weak associations were also found between HIV infection and a history of cocaine use (OR = 2.57; 95% CI = 0.95-7.11; p = 0.039); having more than four clients per night (OR = 5.14; 95% CI = 1.65-16.74; p = 0.04); and a history of receiving treatment for salpingitis (OR = 2.31; 95% CI = .93-5.75; p = 0.0035). No statistically significant association was found between HIV infection and marijuana use nor any sociodemographic variables (age, place of work, and duration of sex work). There is an urgent need for a community based behavioural intervention programme targetting this high risk population.

Use of aromatase inhibitors in the adjuvant treatment of breast cancer

The value of endocrine treatment of early breast cancer has been illustrated by the antioestrogen, tamoxifen, which has now been available for nearly 30 years. However, if the recognised side effects and pharmacological properties of tamoxifen are taken into consideration, it is possible that other endocrine treatments that are now available can provide equal or superior efficacy, along with improved tolerability. One such group of agents is the aromatase inhibitors specifically the new-generation triazole aromatase inhibitors, such as anastrozole and letrozole, which have both shown tolerability and efficacy advantages over standard treatments in postmenopausal women with advanced breast cancer. There are convincing reasons why the new generation of aromatase inhibitors have advantages over tamoxifen. For instance, from their agonist properties, the effects on the endometrium and tumour stimulation seen with tamoxifen would not be expected, nor would the visual disturbances that have been associated with the triphenylethylene compounds, including tamoxifen. A number of aromatase inhibitors, for instance, anastrozole, letrozole and exemestane, are currently being investigated for treatment of early breast cancer. The results of the trials of aromatase inhibitors and tamoxifen will, in the next few years, define whether or not the new-generation aromatase inhibitors have a role to play in the treatment of postmenopausal women with early breast cancer.

Langer's axillary arch in association with sentinel lymph node

Langer's axillary arch is a relatively rare anatomical variation of latissimus dorsi muscle insertion. The clinical importance of this condition in axillary lymph node dissection (ALND) and lymphoedema as well as latissimus dorsi flap reconstruction has been described previously. Axillary vein obstruction in association with this condition has also been reported. We report two cases of Langer's axillary arch encountered during sentinel lymph node (SLN) biopsy which had some bearing on the procedure.

Neonatal rabbit proximal tubule basolateral membrane Na+/H+ antiporter and Cl-/base exchange

The present in vitro microperfusion study examined the maturation of Na+/H+ antiporter and Cl-/base exchanger on the basolateral membrane of rabbit superficial proximal straight tubules (PST). Intracellular pH (pHi) was measured with the pH-sensitive fluorescent dye 2', 7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein in neonatal and adult superficial PST. Na+/H+ antiporter activity was examined after basolateral Na+ addition in tubules initially perfused and bathed without Na+. Neonatal Na+/H+ antiporter activity was approximately 40% that of adult segment (9.7 +/- 1.5 vs. 23.7 +/- 3.2 pmol. mm-1. min-1; P < 0.001). The effect of bath Cl- removal on pHi was used to assess the rates of basolateral Cl-/base exchange. In both neonatal and adult PST, the Cl-/base exchange activity was significantly higher in the presence of 25 mM HCO-3 than in the absence of HCO-3 and was inhibited by cyanide and acetazolamide, consistent with Cl-/HCO-3 exchange. The proton flux rates in the presence of bicarbonate in neonatal and adult tubules were 14.1 +/- 3.6 and 19.5 +/- 3.5 pmol. mm-1min-1, respectively (P = NS), consistent with a mature rate of Cl-/HCO-3 exchanger activity in neonatal tubules. Basolateral Cl-/base exchange activity in the absence of CO2 and HCO-3, with luminal and bath cyanide and acetazolamide, was greater in adult than in neonatal PST and inhibited by bath DIDS consistent with a maturational increase in Cl-/OH- exchange. We have previously shown that the rates of the apical membrane Na+/H+ antiporter and Cl-/base exchanger were approximately fivefold lower in neonatal compared with adult rabbit superficial PST. These data demonstrate that neonatal PST basolateral membrane Na+/H+ antiporter and Cl-/base exchanger activities are relatively more mature than the Na+/H+ antiporter and Cl-/base exchangers on the apical membrane.

On the scientific inference from clinical trials

We have not been able to describe clearly how we generalize findings from a study to our own 'everyday patients'. This difficulty is not surprising, since generalization deals with how empirical observations are related to the growth of scientific knowledge, which is a major philosophical problem. An argument, sometimes used to discard evidence from a trial, is that the patient sample was too selected and therefore not 'representative' enough for the results to be meaningful for generalization. In this paper, we discuss issues of representativeness and generalizability. Other authors have shown that generalization cannot only depend on statistical inference. Then, how do randomized clinical trials contribute to the growth of knowledge? We discuss three aspects of the randomized clinical trial (Mant 1999), First, the trial is an empirical experiment set up to study the intervention on the question as specifically and as much in isolation from other -- biasing and confounding -- factors as possible (Rothman & Greenland 1998). Second, the trial is set up to challenge our prevailing hypotheses (or prejudices) and the trial is above all a help in error elimination (Popper 1992). Third, we need to learn to see new, unexpected and thought-provoking patterns in the data from a trial. Point one -- and partly point two -- refers to the paradigm of the controlled experiment in scientific method. How much a study contributes to our knowledge, with respect to points two and three, relates to its originality. In none of these respects is the representativeness of the patients, or the clinical situations, crucial for judging the study and its possible inferences. However, we also discuss that the biological domain of disease that was studied in a particular trial has to be taken into account. Thus, the inference drawn from a clinical study is not only a question of statistical generalization, but must include a jump from the world of experiences into the world of reason, assessment and theoretical judgement.

Effect of luminal angiotensin II receptor antagonists on proximal tubule transport

The proximal tubule can endogenously synthesize and secrete luminal angiotensin II at a concentration approximately 100- to 1000-fold higher than that in the systemic circulation. We have recently shown that this endogenously produced and luminally secreted angiotensin II regulates proximal tubule volume reabsorption, which is a reflection of sodium transport within this segment. In this study, we use in vivo microperfusion of angiotensin II receptor antagonists into the lumen of the proximal tubule to examine the role of the luminal AT1 and AT2 receptor in the regulation of volume reabsorption. Systemically administered (intravenous) AT1 and AT2 receptor antagonists, acting through basolateral angiotensin II receptors, have previously been shown to inhibit proximal tubule transport. Luminal perfusion of 10(-6) mol/L Dup 753 (AT1 antagonist) and 10(-6) mol/L PD 123319 (AT2 antagonist) decreased proximal tubule volume reabsorption from 2.94 +/- 0.18 to 1.65 +/- 0.18 and 1.64 +/- 0.19 nL/mm x min, respectively, P < .01. Luminal perfusion of 10(-4) mol/L CGP 42112A, another AT2 antagonist, similarly decreased volume reabsorption to 1.32 +/- 0.36 nL/nm x min, P < .01. The inhibition of transport with AT1 and AT2 antagonist was additive, as luminal perfusion of 10(-6) mol/L Dup 753 plus 10(-6) mol/L 123319 resulted in a decrease in volume reabsorption to 0.41 +/- 0.31 nL/mm x min, P < .001 v control, P < .05 v Dup 753, and P < .01 v PD 123319. These results show that endogenously produced angiotensin II regulates proximal tubule volume transport via both luminal AT1 and AT2 receptors.

Increased concentrations of interleukin 1-beta in whole blood cultures supernatants after 12 weeks of moderate endurance exercise

The aim of the study was to investigate whether a regular moderate endurance exercise programme influenced the in vitro cytokine synthesis by stimulated whole blood cultures. To this end, eight healthy subjects exercised moderately by running for 3-5 h a week over a period of 12 weeks, whilst seven other healthy subjects served as the control group. The intensity of the exercise was determined by lactic acid concentrations in the blood which were maintained between 1.8 and 2.5 mmol x l(-1). Over the period of training the running velocity producing the 4 mmol x l(-1) lactic acid threshold increased from 2.86 (SD 0.83) m x s(-1) to 3.06+/-0.79 m x s(-1) (P < or = 0.008). Blood samples were taken at rest before and after the training programme. The following blood parameters were determined: leucocyte count, differential leucocyte count, lymphocyte subpopulations [CD14 positive (+)/CD45+, CD4+/ CD25+, CD8+, CD16+/CD122+]. Whole blood cultures were stimulated with lipopolysaccarides [interleukin (IL)-1 beta and IL-6] and staphylococcal enterotoxin B [IL-2, soluble interleukin 2 receptor (sIL2-R) and interferon (IFN)-gamma]. Cytokine concentrations in the supernatants were measured using an enzyme-linked immunosorbent assay. The white blood cell count, differential leucocyte count, lymphocyte subset distribution and the expression of the CD25 and CD122 antigen on lymphocytes were unchanged by training. After the training programme the IL-1 beta production changed significantly [1496 (SD 264) pg ml(-1) before, compared to 2127 (SD 672) pg ml(-1) after training, P < or = 0.008]. In the control group these parameters remained unchanged. With respect to changes in the values in both groups the syntheses of IL-1 beta (P < or = 0.023) and IL-6 (P < or = 0.021) were significantly higher after regular training. The syntheses of IL-2, sIL-2 and INF-gamma were not significantly influenced. Regular endurance exercise influenced the in vitro production of monocyte derived cytokines, while the effect of exercise on the cytokines synthesized by T-cells appeared to be of lesser importance.

Evaluation of the MRL diagnostics dengue fever virus IgM capture ELISA and the PanBio Rapid Immunochromatographic Test for diagnosis of dengue fever in Jamaica

We evaluated two new commercial dengue diagnostic tests, the MRL Diagnostics Dengue Fever Virus IgM Capture ELISA and the PanBio Rapid Immunochromatographic Test, on serum samples collected during a dengue epidemic in Jamaica. The MRL ELISA method correctly identified 98% (78 of 80) of the samples as dengue positive, while the PanBio test identified 100% (80 of 80). Both tests were 100% (20 samples of 20) specific.

Plasma lycopene concentrations in humans are determined by lycopene intake, plasma cholesterol concentrations and selected demographic factors

Higher plasma lycopene concentrations have been associated with a reduced risk of several chronic diseases. Determinants of lycopene concentrations in humans have received limited attention. We had blood lycopene concentrations and lycopene consumption data available from 111 participants in a two-center cancer prevention trial involving beta-carotene and examined determinants of plasma lycopene levels cross-sectionally. The median plasma lycopene level was 0.59 micromol/L (range 0.07-1.79). Low plasma concentrations of lycopene were associated with the following variables in univariate analyses: study site (Florida lower than Connecticut, P = 0.001), being nonmarried (P = 0.02), having lower income (P = 0.003), being nonwhite race/ethnicity (P = 0.03), having lower dietary lycopene intake (r = 0.29, P = 0.002), having lower plasma cholesterol (r = 0. 43, P = 0.0001) and triglyceride levels (r = 0.26, P = 0.005), and consuming less vitamin C (r = 0.20, P = 0.03). Women had slightly higher plasma lycopene levels than men (0.65 vs. 0.58 micromol/L; P = 0.31), despite lower dietary intake of lycopene (1,040 vs. 1,320 microg/d; P = 0.50). Plasma lycopene levels did not differ in smokers and nonsmokers. In stepwise regression analyses, the determinants of plasma lycopene were plasma cholesterol, dietary lycopene, and marital status; these three variables explained 26% of the variance in plasma lycopene. Relatively few lifestyle and demographic factors were important determinants of plasma lycopene levels, with plasma cholesterol, marital status, and lycopene intake being of greatest importance.

Allelic variation at (TAA)n microsatellite loci in a world collection of chickpea (Cicer arietinum L.) germplasm

A set of 12 randomly selected (TAA)n microsatellite loci of the cultivated chickpea (Cicer arietinum L.) were screened in a worldwide sample comprising 72 landraces, four improved cultivars and two wild species of the primary gene pool (C. reticulatum and C. echinosperum) to determine the level and pattern of polymorphism in these populations. A single fragment was amplified from all the accessions with each of 12 sequence-tagged microsatellite site markers, except for one locus where no fragment was obtained from either of the two wild species. There was a high degree of intraspecific polymorphism at these microsatellite loci, although isozymes, conventional RFLPs and RAPDs show very little or no polymorphism. Overall, the repeat number at a locus (excluding null alleles) ranged from 7 to 42. The average number of alleles per locus was 14.1 and the average genetic diversity was 0.86. Based on the estimates obtained, 11 out of the 12 frequency distributions of alleles at the loci tested can be considered to be non-normal. A significant positive correlation between the average number of repeats (size of the locus) and the amount of variation was observed, indicating that replication slippage may be the molecular mechanism involved in generation of variability at the loci. A comparison between the infinite allele and stepwise mutation models revealed that for 11 out of the 12 loci the number of alleles observed fell in between the values predicted by the two models. Phylogenetic analysis of microsatellite polymorphism in C. arietinum showed no relationship between accession and geographic origin, which is compatible with the recent expansion of this crop throughout the world.

'Should a mammographic screening programme carry the warning: screening can damage your health!'?

The balanced presentation afforded by convening a Citizens' Jury when considering a major question such as the introduction of a breast screening programme is advocated. This method would enable account to be taken of all the costs, both human and financial, to all those affected, both participating and organizing, as well as the benefits. Provision of such a democratic opportunity enables consideration to be given to a broad range of factors, by selection of an appropriate range of witnesses, with the advantage of involving the lay public in this decision-making process. Attendance by health correspondents, medical journalists and other media representatives enables publicization of a democracy in action whilst helping to inform the wider debate. Such an exercise could inform whether the NHS BSP should continue in its current form.

Maturational changes in rabbit renal brush border membrane vesicle urea permeability

Urea transport in the proximal tubule is thought to occur by passive diffusion through the lipid bilayers of the cell membranes. The lipid composition of cell membranes changes during maturation and may directly affect urea permeability of proximal tubule membranes. The present study examined the maturation of urea transport in rabbit renal brush border membrane vesicles (BBMV). BBMV from adult and neonatal (9- to 11-d-old) New Zealand white rabbits were loaded with 500 mM urea and mixed with an iso-osmotic mannitol solution using a stop-flow instrument. Vesicle shrinkage, due to efflux of urea, was followed with light scattering and urea permeability was calculated from an exponential fit of the data. Urea permeability was significantly lower in the neonatal BBMV than the adult at 25 degrees C (0.34+/-0.04 x 10(-6) versus 0.56+/-0.03 x 10(-6) cm/sec;p < 0.001, n=7) and 37 degrees C (0.45+/-0.04 x 10(-6) versus 0.66+/-0.03 x 10(-6) cm/sec; p=0.001, n=7). There was no effect of 250 microM phloretin on urea permeability in either adult or neonatal BBMV at either temperature. The activation energy for urea diffusion was higher in the neonatal than the adult BBMV. Because the maturational increase in urea permeability could potentially be due to a sodium-dependent urea transporter in the adult BBMV, the sodium dependence of urea uptake in adult BBMV was examined. There was no difference in urea permeability in the presence or absence of 20 mM NaCl. Permeability of the lipid-soluble molecule, glycerol, was also found to be the same in the neonatal and adult BBMV. Urea transport in the apical membrane of neonatal and adult proximal tubules is not phloretin sensitive, a finding consistent with diffusion of urea via the lipid bilayer. The rate of urea diffusion is lower in neonatal membranes and may be an important factor in overall urea excretion. This may also play a role in developing and maintaining a high medullary urea concentration and thus the ability to concentrate the urine during renal maturation.

Thyroid hormone stimulates the renal Na/H exchanger NHE3 by transcriptional activation

Thyroid hormone stimulates renal proximal tubule NaCl and NaHCO3 absorption in part by activating the apical membrane Na/H exchanger NHE3. We used a renal epithelial cell line, the opossum kidney (OK) cell, to define the mechanism by which 3,5,3'-triiodothyronine (T3) increases NHE3 activity. T3 stimulated NHE3 activity, an effect that was blocked by inhibition of cellular transcription or translation. The increase in activity was associated with increases in steady-state cell surface and total cellular NHE3 protein and NHE3 transcript abundance. T3 stimulated transcription of the NHE3 gene and had no effect on NHE3 transcript stability. The transcriptional activity of the 5'-flanking region of the rat NHE3 gene was stimulated by T3 when expressed in OK cells. When heterologously expressed rat NHE3 transcript levels were clamped constant with a constitutive promoter in OK cells, T3 has no effect on rat NHE3 protein abundance, suggesting the absence of regulation of NHE3 protein stability or translation. These studies demonstrate that T3 stimulates NHE3 activity by activating NHE3 gene transcription and increasing NHE3 transcript and protein abundance.

The effect of anastrozole on the pharmacokinetics of tamoxifen in post-menopausal women with early breast cancer

Thirty-four post-menopausal women with early breast cancer who had received 20 mg tamoxifen once daily as adjuvant therapy for at least 10 weeks participated in a randomized, double-blind, parallel-group, multicentre trial. The primary aim of the trial was to determine the effect of anastrozole upon tamoxifen pharmacokinetics, with secondary aims of assessing the tolerability of the two drugs in combination and whether or not tamoxifen had any effect upon the oestradiol suppression seen with anastrozole. Patients were randomized to receive either 1 mg anastrozole (16 patients) or matching placebo (18 patients) once daily on a double-blind basis for 28 days. No significant difference (P = 0.919) was observed in serum tamoxifen concentrations between the anastrozole and placebo groups during the trial. The serum concentration of oestradiol was significantly suppressed (P < 0.0001) in patients co-administered anastrozole compared with placebo in the presence of tamoxifen, confirming that anastrozole remained an effective suppressant of oestradiol in the presence of tamoxifen. The combination of tamoxifen and anastrozole was well tolerated, with very little difference in side-effects reported between anastrozole and placebo. In conclusion, the results of this study confirm that anastrozole does not affect the pharmacokinetics of tamoxifen when the two drugs are given in combination to post-menopausal women with early breast cancer. In addition, the oestradiol suppressant effects of anastrozole appear unaffected by tamoxifen.

Association of terminal chromosome 1 deletion with sertoli cell-only syndrome

We report on del(1)(q44), developmental delay, cryptorchidism, and seizure disorder in a 19-year-old man. Endocrinologic evaluation showed delayed puberty and elevated gonadotropins. Testicular biopsy was consistent with Sertoli cell-only syndrome. The case illustrates a previously an unreported manifestation in males with del(1)(q44), and suggests a link between the development of germinal epithelium and genes in the 1q44 area.

Using an interactive video disk in breast cancer patient support

A randomised-controlled trial compared outcomes for women recently diagnosed with breast cancer who either received support and information from a multidisciplinary team or used a shared decision-making programme on an interactive video disk (IVD) system. Using the IVD did not have a significant effect on the decisions women made about treatment, yet it was evaluated positively by those who used it. The results suggest that the role of clinical staff is more significant than the form of information provided. Potential benefits for the IVD were apparent such as standardising the information received by patients, promoting evidence-based practice and providing a measure for quality assurance.

Inhibition of proximal convoluted tubule transport by dopamine

BACKGROUND

Dopamine can produce a natriuresis and diuresis independent of changes in renal hemodynamics. However, previous studies have failed to demonstrate an inhibition of transport by dopamine in intact proximal convoluted tubules.

METHODS

Rabbit proximal convoluted tubules were perfused in vitro with an ultrafiltrate-like solution and bathed in a serum-like albumin solution.

RESULTS

In the present study, the addition of 10-5 M dopamine to the lumen or bath of proximal convoluted tubules perfused in vitro had no effect on transport. In proximal convoluted tubules, addition of 10-6 M bath norepinephrine increased the rate of volume absorption from 0.65 +/- 0.08 to 0.93 +/- 0.08 nl/mm. min (P < 0.01). Addition of 10-5 M luminal dopamine in the presence of bath norepinephrine inhibited the rate of volume absorption to 0.72 +/- 0.10 nl/mm. min (P = 0.01). The inhibition in the rate of volume absorption by luminal dopamine in the presence of bath norepinephrine was completely blocked by the DA1 antagonist, SCH 23390. The DA1 agonist luminal 10-5 M fenoldopam also inhibited volume absorption in the presence of bath norepinephrine, but the DA2 agonist luminal 10-5 M quinpirole was without effect. Bath 10-5 M dopamine had no effect on volume absorption in the presence of bath norepinephrine.

CONCLUSION

Dopamine has no direct epithelial action on the proximal convoluted tubule. However, luminal dopamine antagonizes the stimulation in transport produced by norepinephrine. These studies suggest that luminal dopamine may play a role to modulate sodium transport in the presence of renal nerve activity.

Self-reported infectious mononucleosis and 6 cancers: a population-based, case-control study

A study was undertaken to estimate the magnitude of association between self-reported infectious mononucleosis (IM) and 6 types of cancer, including Hodgkin's disease, non-Hodgkin's lymphoma, nasopharyngeal cancer, nasal cancer, primary liver cancer, and sarcoma. Cases were male, aged 15-39 y in 1968, who lived in 8 cancer registry areas. Controls were men selected by random-digit telephone dialing. Cases included 1511 persons with non-Hodgkin's lymphoma, 343 with Hodgkin's disease, 386 with sarcoma and 168, 113 and 70 with primary liver, nasopharyngeal and nasal cancers, respectively. There were 1910 controls. For the 6 cancers combined, the overall odds ratio for IM occurring < 5 and > or = 5 y of the reference date were 5.40 [95% (Confidence Interval (CI) = 1.61, 18.09] and 1.08 (0.84, 1.40), respectively. Analogous values were 4.59 (1.25, 16.85) and 1.07 (0.78, 1.48) for non-Hodgkin's lymphoma and 7.49 (1.52, 36.92) and 1.35 (0.87, 2.09) for Hodgkin's disease. There was the suggestion of a protective association with IM occurring > or = 5 y before cancer onset for the 4 non-lymphomatous cancers. Strongly positive associations between self-reported IM and 6 types of cancer were observed for IM occurring < 5 y before the onset of cancer. There was a suggestion, which is noted with extreme caution, that IM earlier in life might have had a protective association with the 4 non-lymphomatous cancers.

Effect of supplemental beta-carotene on plasma concentrations of carotenoids, retinol, and alpha-tocopherol in humans

High doses of beta-carotene, a lipid-soluble nutrient, may affect the plasma concentrations of other lipid-soluble nutrients. The purpose of this study was to assess the effects of long-term daily supplementation with beta-carotene (50 mg/d) on circulating concentrations of other carotenoids, retinol, and alpha-tocopherol over time. Data were available from 259 men and women participating in the Carotene Prevention Trial, a 2-center chemoprevention trial designed to determine whether supplemental beta-carotene can prevent second malignant tumors in patients cured of an early stage cancer of the oral cavity, pharynx, or larynx. Up to 2 blood samples were obtained before the intervention (before and after a 1-mo placebo run-in), with postrandomization samples obtained at 3, 12, 24, 36, 48, and 60 mo. Supplementation with beta-carotene produced a persistent 9- to 10-fold increase in median plasma beta-carotene concentrations (225 nmol/L at baseline to 2255 nmol/L at 3 mo) and a persistent 2-fold increase in median plasma alpha-carotene concentrations (45 nmol/L at baseline to 95 nmol/L at 3 mo). Concentrations of retinol, alpha-tocopherol, lycopene, and lutein/zeaxanthin were not affected by supplemental beta-carotene. Up to 5 y of daily supplementation with beta-carotene increased circulating concentrations of alpha- and beta-carotene, but did not alter concentrations of lycopene, lutein/zeaxanthin, retinol, or alpha-tocopherol.

Tamoxifen--the treatment of choice. Why look for alternatives?

Tamoxifen is currently established as the endocrine treatment of choice in breast cancer. In advanced breast cancer, response rates of up to 60% in women with oestrogen receptor (ER)-positive tumours have been reported. In early breast cancer, tamoxifen can produce significant benefits, both statistically and clinically, in terms of reduction in relative risk of relapse or death in all patient subgroups (i.e. ER status, aged < or > 50 years) except premenopausal women with ER-negative tumours. The major benefit, however, is seen in women over 50 years old with ER-positive tumours. The results of randomized trials suggest that the optimum duration of tamoxifen therapy is at least 5 years. Two large pragmatic trials (aTTom and ATLAS) are under way to determine whether additional benefit can be gained from continuing tamoxifen treatment beyond 5 years. Recent data also suggest possible synergism between tamoxifen and chemotherapy in the treatment of early breast cancer in post-menopausal women. Other benefits of tamoxifen treatment include reduction in the risk of developing contralateral breast cancer. Included among the non-breast cancer benefits of tamoxifen are reduced risk of cardiovascular disease and protection against bone loss in post-menopausal women. These benefits must be weighed against the possible increased incidence of endometrial cancer. Notwithstanding its undoubted success, there is a need for agents to improve upon tamoxifen. Newer agents, such as the luteinizing hormone-releasing hormone analogue goserelin and the new-generation aromatase inhibitors, such as anastrozole, will add new life to the search for an improved endocrine therapy for early breast cancer.

Bone mineral density in children with myelomeningocele

BACKGROUND

Difficulties with ambulation in patients with myelomeningocele often lead to physical inactivity, osteoporosis, and subsequent development of pathologic fractures.

OBJECTIVE

The purpose of this study was to examine bone mineral density and biochemical markers of bone metabolism in patients with myelomeningocele.

DESIGN AND METHODS

A total of 35 patients between 6 and 19 years of age with myelomeningocele (ambulatory and nonambulatory) were randomly chosen at the Texas Scottish Rite Hospital for Children. We measured bone mineral density of the distal radius in these patients using single photon absorptiometry and measured the biochemical markers of bone metabolism including parathyroid hormone, 1,25 vitamin D, osteocalcin, urinary pyridinolines/deoxypyridinolines, and urinary calcium excretion.

RESULTS

Bone mineral density of the distal radius in the patients with myelomeningocele was approximately 1 to 2 standard deviation units below the mean of the normal population. There were no significant differences between ambulators and nonambulators. However, bone mineral density of the 8 patients who suffered multiple fractures (19) was significantly lower than that for those remaining patients without fractures. Elevated urinary pyridinoline levels, which indicate elevated bone reabsorption, were found more frequently in both non- and limited ambulators than in full-time ambulators. Urinary calcium excretion also was greater than twofold higher in nonambulatory patients versus ambulatory patients. There were no other differences in the biochemical markers of bone metabolism (osteocalcin, parathyroid hormone, 1,25 vitamin D, and urinary deoxypyridinolines) between ambulators and nonambulators. Bone mineral density rises in normal growing children 6 to 19 years of age. When the boys and girls were considered separately, bone mineral density rises with age in boys, but not in girls.

CONCLUSION

Patients with myelomeningocele have decreased bone mineral density and are at risk of suffering pathologic bone fractures. The measurement of bone mineral density may help to identify those patients at greatest risk of suffering multiple fractures. The urinary calcium excretion of nonambulators was higher than that of ambulators and likely contributes to their decreased bone mineral density. Bone mineral density increases with age in boys, but not in girls.

Renal Na/H exchanger NHE-3 and Na-PO4 cotransporter NaPi-2 protein expression in glucocorticoid excess and deficient states

Administration of pharmacologic doses of glucocorticoid in vivo increases renal proximal tubule apical membrane Na/H exchange and decreases Na/PO4 cotransport activity (1). Current data suggest that the NHE-3 and NaPi-2 proteins mediate significant fractions of proximal tubule apical membrane Na/H exchange and Na/PO4 cotransport, respectively. This study examines whether glucocorticoid excess or deficiency affects NHE-3 and NaPi-2 protein abundance and the intrarenal distribution of these transporters. Protein abundance of NHE-3 and NaPi-2 in control rats was compared to rats rendered glucocorticoid-deficient by bilateral adrenalectomy, and to rats receiving pharmacologic doses of dexamethasone using immunoblots and immunohistochemistry. Adrenalectomy had modest effects on NHE-3 protein abundance, but dexamethasone administration to either adrenalectomized or sham-operated rats significantly increased NHE-3 protein abundance in both the proximal tubule and thick ascending limb, but not the thin descending limb. Adrenalectomy increased NaPi-2 protein abundance in the proximal tubule, whereas dexamethasone administration dramatically suppressed NaPi-2 protein on the apical membrane in both adrenalectomized and sham-operated animals. No significant reciprocal increase in subapical NaPi-2 staining was seen in the dexamethasone-treated rats. The present study shows that glucocorticoids regulate proximal tubule apical membrane Na/H exchange and NaPi cotransport by changes in protein abundance of NHE-3 and NaPi-2, respectively.

Human herpesvirus 8 as a potential sexually transmitted agent in Honduras

The seroprevalence of human herpesvirus 8 (HHV-8) was studied in 326 human immunodeficiency virus (HIV)-positive and -negative persons from Honduras; women constituted 77% (n = 251) of the subjects. Sera were tested for lytic HHV-8 antibodies by an IFA, and positive samples were confirmed by a radioimmunoprecipitation assay. Of the 326 persons tested, 58 (17.8%) had HHV-8 antibodies. Among the HIV-infected women, 22.7% were seropositive; 11.3% of the HIV-negative women were seropositive. HHV-8 seroprevalence was almost four times higher in HIV-positive female commercial sex workers (36%) than in HIV-negative female non-commercial sex workers (9.9%; odds ratio = 3.8, 95% confidence interval = 1.1-13; P = 0.01), suggesting that commercial sex work is a risk factor for HHV-8 infection. In the men studied, the overall HHV-8 seroprevalence was 22.6%, with a seropositivity rate of 28% for HIV-positive men compared with 12% for HIV-negative men.

Campaign strategy and tactics for clinical trials in surgical oncology

The strategic planning of the campaign against cancer and the employment of clinical trials on a national and supranational basis could be improved. Lessons and principles derived from other spheres of ordered activity might be usefully applied to the realm of clinical trials. Principles taught by military strategists may find practical applications in the development and prosecution of successful clinical trials of cancer therapy. In this paper we reflect upon the parallels and divergences between the principles of campaign strategy needed for the successful prosecution of military objectives and the efficient and effective prosecution of major clinical trials.

The Fanconi syndrome of cystinosis: insights into the pathophysiology

Cystinosis is a lysosomal storage disease which is the most-common inherited cause of the Fanconi syndrome. Insights into the pathophysiology of the proximal tubular defect have come from in vitro studies of the cystine-loaded tubule. Proximal tubules loaded with cystine have a generalized proximal tubule transport defect characteristic of the Fanconi syndrome. The decrease in proximal tubular transport with cystine loading is not due to an increase in paracellular permeability with backflux of solute transport from the blood to the tubular lumen, but due to a decrease in active transport. The Na-K-ATPase activity is intact under Vmax conditions in cystine-loaded tubules; however, the production of ATP is severely compromised. The cystine-loaded tubule has a lower intracellular phosphate concentration than that of control tubules. This low intracellular phosphate concentration in cystine-loaded tubules likely plays a critical role in the decrease in intracellular ATP. Preservation of intracellular phosphate at control levels prevents the decrease in intracellular ATP and the proximal tubule respiratory dysfunction with cystine loading. The clinical significance and future directions for investigation are discussed.

Maturational changes in rabbit renal brush border membrane vesicle osmotic water permeability

We have recently shown that the osmotic water permeability (Pf) of proximal tubules from neonatal rabbits is higher than that of adults (AJP 271:F871-F876, 1996). The developmental change in Pf could be due to differences in one or more of the components in the path for transepithelial water transport. The present study examined developmental changes in water transport characteristics of the proximal tubule apical membrane by determining Pf and aquaporin 1 (AQP1) expression in neonatal (10-14 days old) and adult rabbit renal brush border membrane vesicles (BBMV). AQP1 abundance in the adult BBMV was higher than the neonatal BBMV. At 25 degrees C the Pf of neonatal BBMV was found to be significantly lower than the adult BBMV at osmotic gradients from 50 to 250 mOsm/kg water. The activation energy for osmotic water movement was higher in the neonatal BBMV than the adult BBMV (9.19 +/- 0.37 vs. 5.09 +/- 0.57 kcal . deg-1 . mol-1, P < 0.005). Osmotic water movement in neonatal BBMV was inhibited 17.9 +/- 1.3% by 1 mm HgCl2 compared to 34.3 +/- 3.8% in the adult BBMV (P < 0.005). These data are consistent with a significantly greater fraction of water traversing the apical membrane lipid bilayer in proximal tubules of neonates than adults. The lower Pf of the neonatal BBMV indicates that the apical membrane is not responsible for the higher transepithelial Pf in the neonatal proximal tubule.

Endogenous angiotensin II modulates rat proximal tubule transport with acute changes in extracellular volume

In the present study, we examined whether the effect of endogenously produced angiotensin II on proximal tubule transport in the male Sprague-Dawley rat is regulated by acute changes in extracellular volume. We measured the magnitude of endogenous angiotensin II-mediated stimulation of transport by sequentially perfusing proximal tubules in vivo, first with an ultrafiltrate-like solution, then by reperfusion of the same tubule with an ultrafiltrate-like solution containing 10(-8) M losartan (angiotensin II receptor antagonist). During volume contraction, 10(-8) M losartan decreased volume reabsorption from 4.20 +/- 0.50 to 1.70 +/- 0.30 nl . mm-1 . min-1 (P < 0.05), a decrease of 58.0 +/- 7.0%. In contrast, after acute volume expansion, 10(-8) M losartan decreased volume reabsorption from 1.84 +/- 0.20 to 1.31 +/- 0.20 nl . mm-1 . min-1 (P < 0.05), a decrease of 29.6 +/- 9.0%. In hydropenic rats, addition of exogenous luminal angiotensin II had no effect on transport. However, in volume-expanded rats, addition of 10(-8) M angiotensin II increased volume reabsorption from 2.10 +/- 0.34 to 4. 38 +/- 0.59 nl . mm-1 . min-1 (P < 0.005). These data are consistent with endogenously produced angiotensin II augmenting proximal tubule transport to a greater degree during volume contraction than after volume expansion.

Mild cognitive impairment and risk of mortality in HIV-1 infection

HIV-1-associated cognitive impairment has only been preliminarily investigated for associations with mortality. The authors examined 119 HIV-1-positive homosexual men (asymptomatic: n = 96; early symptomatic: n = 23). At follow-up (to 3.5 years), there were 105 survivors and 14 nonsurvivors. Those at the 25th percentile in response speeds and in long-term memory retrieval accuracy were at 6.4 (P < 0.02) and 3.5 (P < 0.05) times increased mortality risk, respectively, of those at the 75th percentile--independent of baseline CDC clinical stage, CD4 cell count, hemoglobin level, antiretroviral and prophylactic medication use, and sociodemographics. Cognitive impairment should be identified early--for maximization of both functional status and survival time.