Control of Proximal Bicarbonate Reabsorption in Normal and Acidotic Rats

This free-flow micropuncture study examined the dependence of bicarbonate reabsorption in the rat superficial proximal convoluted tubule to changes in filtered bicarbonate load, and thereby the contribution of the proximal tubule to the whole kidney's response to such changes. The independent effects of extracellular fluid (ECF) volume expansion and of acidosis on proximal bicarbonate reabsorption were also examined.When the plasma volume contraction incurred by the micropuncture preparatory surgery was corrected by isoncotic plasma infusion ( congruent with1.3% body wt), single nephron glomerular filtration rate (SNGFR), and the filtered total CO(2) load increased by 50%. Absolute proximal reabsorption of total CO(2) (measured by microcalorimetry) increased by 30%, from 808+/-47 during volume contraction to 1,081+/-57 pmol/min.g kidney wt after plasma repletion, as fractional total CO(2) reabsorption decreased from 0.90 to 0.77. Aortic constriction in these plasma-repleted rats returned the filtered load and reabsorption of total CO(2) to the previous volume contracted levels. In other animals isohydric ECF expansion with plasma (5% body wt) or Ringer's solution (10% body wt), or both, produced no further diminution in fractional proximal total CO(2) reabsorption (0.76-0.81).Metabolic acidosis was associated with very high fractional proximal total CO(2) reabsorptive rates of 0.82 to 0.91 over a wide range of SNGFR and ECF volumes. At a single level of SNGFR, end-proximal total CO(2) concentration progressively decreased from 5.6+/-0.5 to 1.6 +/-0.2 mM as arterial pH fell from 7.4 to 7.1. Expansion of ECF volume in the acidotic rats did not inhibit the ability of the proximal tubule to lower end-proximal total CO(2) concentrations to minimal levels.In conclusion, bicarbonate reabsorption in the superficial proximal convoluted tubule is highly load-dependent (75-90%) in normal and acidotic rats. No inhibitory effect of ECF volume per se on proximal bicarbonate reabsorption, independent of altering the filtered bicarbonate load, could be discerned. Acidosis enabled the end-proximal luminal bicarbonate concentration to fall below normal values and reduced distal bicarbonate delivery.     

Axial heterogeneity of bicarbonate, chloride, and water transport in the rat proximal convoluted tubule. Effects of change in luminal flow rate and of alkalemia.

These studies examined regulation of superficial proximal convoluted tubule (PCT) transport as a function of length. When single nephron glomerular filtration rate (SNGFR) increased from 28.7 +/- 0.7 nl/min in hydropenia to 41.5 +/- 0.4 nl/min in euvolemia, bicarbonate, chloride, and water reabsorption in the early (1st mm) PCT increased proportionally: from 354 +/- 21 peq/mm X min, 206 +/- 55 peq/mm X min, and 5.9 +/- 0.4 nl/mm X min to 520 +/- 12 peq/mm X min, 585 +/- 21 peq/mm X min, and 10.1 +/- 0.4 nl/mm X min, respectively. These high transport rates did not increase further, however, when SNGFR went to 51.2 +/- 0.7 or 50.7 +/- 0.6 nl/min after atrial natriuretic factor or glucagon administration. Anion and water transport rates in the late PCT were lower and exhibited less flow dependence. During chronic metabolic alkalosis, acidification was inhibited in the late but not early PCT. In conclusion, the early PCT is distinguished from the late PCT by having high-capacity, flow-responsive but saturable, anion- and water-reabsorptive processes relatively unaffected by alkalemia.     

A mutual information analysis of neural coding of speech by low-frequency MEG phase information

Recent work has implicated low-frequency (<20 Hz) neuronal phase information as important for both auditory (<10 Hz) and speech [theta (～4-8 Hz)] perception. Activity on the timescale of theta corresponds linguistically to the average length of a syllable, suggesting that information within this range has consequences for segmentation of meaningful units of speech. Longer timescales that correspond to lower frequencies [delta (1-3 Hz)] also reflect important linguistic features-prosodic/suprasegmental-but it is unknown whether the patterns of activity in this range are similar to theta. We investigate low-frequency activity with magnetoencephalography (MEG) and mutual information (MI), an analysis that has not yet been applied to noninvasive electrophysiological recordings. We find that during speech perception each frequency subband examined [delta (1-3 Hz), theta(low) (3-5 Hz), theta(high) (5-7 Hz)] processes independent information from the speech stream. This contrasts with hypotheses that either delta and theta reflect their corresponding linguistic levels of analysis or each band is part of a single holistic onset response that tracks global acoustic transitions in the speech stream. Single-trial template-based classifier results further validate this finding: information from each subband can be used to classify individual sentences, and classifier results that utilize the combination of frequency bands provide better results than single bands alone. Our results suggest that during speech perception low-frequency phase of the MEG signal corresponds to neither abstract linguistic units nor holistic evoked potentials but rather tracks different aspects of the input signal. This study also validates a new method of analysis for noninvasive electrophysiological recordings that can be used to formally characterize information content of neural responses and interactions between these responses. Furthermore, it bridges results from different levels of neurophysiological study: small-scale multiunit recordings and local field potentials and macroscopic magneto/electrophysiological noninvasive recordings.     

Wegener's granulomatosis overlapping with Takayasu's arteritis revealed by FDG-PET scan

We report the case of a 23-year-old woman who initially presented with Wegener's granulomatosis (WG) limited to the lungs, diagnosed on the basis of a biopsy of an upper left lobe nodule and elevated ANCA titers. Remission occurred under treatment with methylprednisolone and intravenous immunoglobulins. Later in the course of the disease, findings highly suggestive of Takayasu's arteritis (TA) appeared: murmur at the level of the left subclavian artery, thickening of the arterial wall of the aorta and pulmonary arteries on tomodensidometry, and abnormal uptake of the aortic arch and ascending aorta on FDG-PET scan. This latter exam also showed an increased uptake of an already known pulmonary nodule, due to WG. Although five cases of WG occurring together with TA have previously been reported, this is the only one in which TA was revealed by FDG-PET scan. In the specific setting of overlapping vasculitides, FDG-PET scan may be helpful in simultaneously evaluating the activity of the two diseases.     

Job of the Bible: leprosy or scabies?

Proposing a medical diagnosis a posteriori of a person who died a long time ago is not as impossible as it sounds if sufficient medical history is available.A whole book of the Bible is devoted to Job and his trials. The diagnosis of leprosy has been generally accepted by medieval commentators because the verses of the Book speak of ulcers disseminated over the skin, and also because leprosy is an exemplary sanction imposed by way of example by God to punish those who have committed a sin. In this paper, we have taken the different verses with a medical content from the Book of Job, and reconstructed the clinical picture as if the patient had turned up in the 21st century in order to see if the diagnosis of leprosy may be called into question, and to discuss the limits of the medico-historic approach. The clinical picture of the disease consists of deterioration in the general condition, with widespread pain, confusion, skin eruptions, bilious vomiting, and so on. Under these conditions, if Job did exist, and if the retrospective medical history is reliable, the most likely diagnosis is that of scabies rather than leprosy.     

Parents Dealing with Anorexia Nervosa: Actions and Meanings

This paper examines parents’ actions in response to anorexia nervosa, and how these are shaped by the ways they construct or understand the eating disorder. The findings indicate that parents try to influence their daughters by searching for help, providing practical support, avoiding confrontation, complying with special requirements, persuading, explaining, and pressuring, using ploys and force, providing emotional support, and mediating interactions. Parents’ actions are influenced by how they construct anorexia, such as whether they see it as an eating issue, an illness, a psychological problem, a choice, or a mystery. Understanding parents’ actions and constructions can help clinicians develop collaborative partnerships with parents.