Sodium reabsorption by the Henle loop in humans

In a previous study, we described a new method [3] to measure Na reabsorption by each segment of the human nephron independently. Reabsorption was expressed as equivalent volumes of solute-free water (CH2O) generated by the loop of Henle (CH2O-HL) and by the distal tubule (CH2O-DT), and dissipated by back diffusion (BD) across collecting ducts (CH2O-BD). These data were obtained during maximal water diuresis (MWD). The present study was undertaken to calculate CH2O-HL by experiments performed during maximal antidiuresis (MA). For this purpose, a new theoretical approach was devised, described by algebraic equations which allowed calculations of segmental transport during MA alone, where only CH2O-HL could be calculated independently. The study was performed on 14 normal volunteers who were studied twice by clearance measurements, firstly during MWD and again during MA. In each experiment, clearance periods were performed during baseline conditions and during the administration of furosemide (0.7 mg/kg bolus injection followed by 0.06 mg/kg/min maintenance infusion). From the values measured during either condition, segmental reabsorption was calculated. During MWD, CH2O-HL averaged 19.4 + 10.4, during MA 20.4 + 8.0 ml/min/GFR X 100; p greater than 0.05. The paired measurements were significantly correlated (r = 0.80; p less than 0.01). These data demonstrate that CH2O-HL obtained with the original theory is a reproducible result that can be confirmed with independent measurements obtained during different experimental conditions. Thus, measurements of segmental Na transport in the human nephron are feasible and can contribute important informations on disease states.     

Consistency of nephron filtration measurements by collection of total tubular fluid from different proximal sites

The stability of single nephron glomerular filtration rate (SNGFR) is assured by specific mechanisms such as the tubulo-glomerular feedback system and autoregulation. Studies on renal physiology rely heavily on the measurements of SNGFR, which are feasible only in animals. The measurement of SNGFR by collection of total tubular fluid may be influenced by the fall in intratubular hydrostatic pressure that may reflect the negative pressure applied to the sampling pipette. This effect may become more important with shortening of the distance between the sampling site and the Bowman space. We analysed this putative effect by performing collections of total tubular fluid from the late proximal (LP), and then from the early proximal (EP) segment of the same nephrons. In 128 paired collections LP-SNGFR averaged 35 (SEM 2) nl?·?min^?1, and was no different from the paired mean EP-SNGFR of 37 (SEM 2) nl?·?min^?1, P>0.179. Then EP- and LP- SNGFR were significantly correlated (r=0.77, P<0.001). As expected, the respective paired means of absolute and percentage reabsorptions, and those of collection rates were significantly different. The average SNGFR computed from each LP and EP paired measurement was significantly correlated with the simultaneously measured kidney glomerular filtration rate, GFR (r=0.60, P<0.0001). The ratio of GFR to SNGFR indicated the expected number of glomeruli. These data would indicate that the sampling site does not influence the measurement of SNGFR in the proximal tubule when the total fluid collection technique is correctly performed. They also exclude a time-dependent activation of the macula densa capable of upregulating SNGFR within the interval elapsing between the beginning of LP and the completion of EP collections, which in our study averaged 4.4 (SEM 0.1) min.     

A phase II study of sulofenur,a novel sulfonylurea,in recurrent epithelial ovarian cancer

Summary A total of 16 patients with recurrent epithelial ovarian cancer were treated with sulofenur (LY 186641), a novel oral sulfonylurea. All subjects had received previous chemotherapy. Anaemia occurred in all 16 patients, 14 of whom required a blood transfusion, and 2/16 patients received methylene blue for breathlessness due to methaemaglobinaemia. Treatment was discontinued in 2/16 cases due to rising liver enzyme values, which reverted to normal on cessation of the drug. There was no nausea or alopecia. Only two minor responses were seen. Plasma drug levels were insufficient to result in antitumour activity as extrapolated from animal data. Further studies that attempt to increase the bioavailability and improve the therapeutic index are warranted.     

Effect of omega-3 fatty acids on rectal mucosal cell proliferation in subjects at risk for colon cancer.

The effects of 12 weeks of omega-3 fatty acid supplementation on rectal mucosal proliferation were assessed with [3H]thymidine autoradiography in a double-blind, placebo-controlled study of 20 patients with sporadic adenomatous colorectal polyps. In the group of 10 that received fish oil containing eicosapentaenoic acid (4.1 g/day) and docosahexaenoic acid (3.6 g/day), the mean percentage of replicative "S"-phase cells in the upper part of colonic crypts (considered a reliable marker of colon cancer risk) significantly dropped from the baseline level after only 2 weeks of treatment and remained lower throughout the study period; no change in upper-crypt labeling was observed in the 10 placebo patients. Rectal mucosal eicosapentaenoic acid content increased in fish oil patients, whereas arachidonic acid levels decreased. The fish oil-induced kinetic changes represent contraction of the proliferative compartment to the levels of a low-risk population and may be related to omega-3 fatty acid effects on the arachidonic prostaglandin pathway. In this short-term trial, fish oil appeared to exert a rapid effect that may protect high-risk subjects from colon cancer.     

Linkage of the MHC to familial multiple sclerosis suggests genetic heterogeneity. The Multiple Sclerosis Genetics Group

Multiple sclerosis (MS) is a demyelinating autoimmune disease of the central nervous system. While its etiology is not well understood, genetic factors are clearly involved. Until recently, most genetic studies in MS have been association studies using the case-control design testing specific candidate genes and studying only sporadic cases. The only consistently replicated finding has been an association with the HLA-DR2 allele within the major histocompatibility complex (MHC) on chromosome 6. Using the genetic linkage design, however, evidence for and against linkage of the MHC to MS has been found, fostering suggestions that sporadic and familial MS have different etiologies. Most recently, two of four genomic screens demonstrated linkage to the MHC, although specific allelic associations were not tested. Here, a dataset of 98 multiplex families was studied to test for an association to the HLA-DR2 allele in familial MS and to determine if genetic linkage to the MHC was due solely to such an association. Three highly polymorphic markers (HLA-DR, D6S273 and TNFbeta) in the MHC demonstrated strong genetic linkage (parametric lod scores of 4.60, 2.20 and 1.24, respectively) and a specific association with the HLA-DR2 allele was confirmed (TDT; P < 0.001). Stratifying the results by HLA-DR2 status showed that the linkage results were limited to families segregating HLA-DR2 alleles. These results demonstrate that genetic linkage to the MHC can be explained by the HLA-DR2 allelic association. They also indicate that sporadic and familial MS share a common genetic susceptibility. In addition, preliminary calculations suggest that the MHC explains between 17 and 62% of the genetic etiology of MS. This heterogeneity is also supported by the minority of families showing no linkage or association with loci within the MHC.      

The effect of carbon dioxide in the airways and alveoli on ventilation; a vagal reflex studied in the dog

1. The inhalation of CO(2) produces a tachypnoea only in the presence of intact vagus nerves; the present study was designed to examine the mechanism of this phenomenon in the dog.2. Closed-chest cardiopulmonary bypass was established in dogs weighing 16-24 kg, anaesthetized with chloralose. When the ;bypass' was established pulmonary blood flow ceased, P(A, CO2) was reduced and the respiratory rate slowed. 3-10% CO(2) in O(2) could then be inhaled without change in the level of P(a, CO2) set at the oxygenator.3. The addition of CO(2) in these concentrations to the inspired oxygen resulted in an increase in respiratory frequency, maximal at the first breath and sustained for the 1 min period of exposure. The increase in respiratory frequency was due to a shortening of expiratory duration. Inspiratory duration did not change. The response was absent after vagotomy.4. Inert gases in O(2), given as a control, had no effect on breathing.5. The effect of raising P(a, CO2) (by increasing the concentration of CO(2) in the gas equilibrating the blood in the oxygenator), was primarily to increase tidal volume.6. The ventilatory effect of inspiring CO(2)/O(2) mixtures was shown to be additive to the effect of raising P(a, CO2).7. These experiments show that an afferent vagal reflex originating from the lungs causes tachypnoea, when a dog, on ;bypass', inhales low concentrations of CO(2) in O(2).     

Localized lymphatic sporotrichosis after fish-induced injury (Tilapia sp.).

Localized lymphatic sporotrichosis generally develops after the fungus Sporothrix schenckii is traumatically introduced into skin or mucosa by contaminated plant material. An 18-year-old male fisherman was injured by spines of the dorsal fin of a fish on the left third finger. The lesion became ulcerated, edematous and suppurative and did not respond to tetracycline and cephalexin. Fifteen days after the accident, a nodular lymphangitic pattern of swelling was observed. Histopathological findings and an intradermal test were suggestive of sporotrichosis and mycological cultures confirmed the diagnosis. The lesions resolved after oral treatment with potassium iodide. Sporotrichosis is a common subcutaneous mycosis in Brazil, and there is a previous report in the literature of this disease being acquired via trauma involving fish spines.     

"Affinity maturation" of ligands for HCV-specific serum antibodies

We have previously screened a phage-displayed random peptide library using sera from patients and identified ligands binding to antibodies specifically associated with the hepatitis C virus infection. The ability of these peptides to detect HCV-specific antibodies was improved through an in vitro procedure which mimics the natural process of antibody affinity maturation operating in secondary immune response. Libraries were generated by mutating the sequence of the original peptide through a protocol that efficiently introduced substitution, insertion and deletion mutations on a single or population of clones. Screening these libraries isolated mutants that displayed increased specific reactivity with a broader range of sera from HCV-infected patients. Several variants of the original peptide were identified which discriminate between the various components of the specific polyclonal response. This methodology to select artificial ligands from RPL using sera and to enhance their diagnostic properties by affinity maturation makes the development of a diagnostic assay to detect disease-associated antibodies feasible, without requiring the natural antigen.