THE POLARITY OF THE PROXIMAL TUBULE CELL IN RAT KIDNEY : Different Surface Charges for the Brush-Border Microvilli and Plasma Membranes from the Basal Infoldings

Two different membrane fractions were obtained from a brush-border fraction of rat kidney cortex by using their different electrical surface charges in preparative free-flow electrophoresis. One membrane fraction contained only morphologically intact microvilli and was characterized by a high specific activity of alkaline phosphatase. The other fraction morphologically resembled classical plasma membranes by possessing junctional complexes and a high Na-K-ATPase activity The contamination of the isolated membrane fractions by other cell organelles was extremely low These two fractions represent the apical (luminal) and the basal (interstitial) area of the renal proximal tubule cell membrane and clearly demonstrate the polarity of this cell

Vitalism in contemporary chiropractic: a help or a hinderance?

Background: Chiropractic emerged in 1895 and was promoted as a viable health care substitute in direct competition with the medical profession. This was an era when there was a belief that one cause and one cure for all disease would be discovered. The chiropractic version was a theory that most diseases were caused by subluxated (slightly displaced) vertebrae interfering with “nerve vibrations” (a supernatural, vital force) and could be cured by adjusting (repositioning) vertebrae, thereby removing the interference with the body’s inherent capacity to heal. DD Palmer, the originator of chiropractic, established chiropractic based on vitalistic principles. Anecdotally, the authors have observed that many chiropractors who overtly claim to be “vitalists” cannot define the term. Therefore, we sought the origins of vitalism and to examine its effects on chiropractic today. Discussion: Vitalism arose out of human curiosity around the biggest questions: Where do we come from? What is life? For some, life was derived from an unknown and unknowable vital force. For others, a vital force was a placeholder, a piece of knowledge not yet grasped but attainable. Developments in science have demonstrated there is no longer a need to invoke vitalistic entities as either explanations or hypotheses for biological phenomena. Nevertheless, vitalism remains within chiropractic. In this examination of vitalism within chiropractic we explore the history of vitalism, vitalism within chiropractic and whether a vitalistic ideology is compatible with the legal and ethical requirements for registered health care professionals such as chiropractors. Conclusion: Vitalism has had many meanings throughout the centuries of recorded history. Though only vaguely defined by chiropractors, vitalism, as a representation of supernatural force and therefore an untestable hypothesis, sits at the heart of the divisions within chiropractic and acts as an impediment to chiropractic legitimacy, cultural authority and integration into mainstream health care

Herbal Diuretics Revisited: From 'Wise Women' to William Withering

This contribution summarizes the use of herbal diuretics over the period of two thousand years. After describing the role of herbs in the framework of the theory of the balance of humors for well-being, it details the contributions of Pliny the Elder (23-79), Dioscorides (40-90), Hildegard von Bingen (1098-1179), Pietro Andrea Matthioli (1500-1577), and Leonard Fuchs (1501- 1566) in providing increasingly more precise descriptions and illustrations of medicinal plants. Then, William Withering's (1741-1799) scientific analysis of the use of foxglove for the treatment of dropsy is presented, taking into account the role peasant 'wise women' played in his discoveries and the role of 'folklore medicine' before him. Copyright (C) 2002 S. Karger AG, Bas

Further evidence for the existence of an intrinsic bicarbonate-stimulated Mg²⁺-ATPase in brush border membranes isolated from rat kidney cortex

The aim of this study was to provide further evidence for the existence of a nonmitochondrial bicarbonate-stimulated Mg2+-ATPase in brush border membranes derived from rat kidney cortex. A plasma membrane fraction rich in brush border microvilli and a mitochondrial fraction were isolated by differential centrifugation. Both fractions contain a Mg2+-ATPase activity which can be stimulated by bicarbonate. The two Mg2+-ATPases are stimulated likewise by chloride, bicarbonate, and sulfite or inhibited by oligomycin and aurovertin, though to different degrees. In contrast to these similarities, only the Mg2+-ATPase activity of the mitochondrial fraction is inhibited by atractyloside, a substance which blocks an adenine nucleotide translocator in the inner mitochondrial membrane. On the other hand, filipin, an antibiotic that complexes with cholesterol in the membranes inhibits exclusively the Mg2+-ATPase of the cholesterol-rich brush border membranes. Furthermore it could be demonstrated by the use of bromotetramisole, an inhibitor of alkaline phosphatase activity, that the Mg2+-ATPase activity in the membrane fraction is not due to the presence of the highly active alkaline phosphatase in these membranes. These results support the assumption that an intrinsic bicarbonate-stimulated Mg2+-ATPase is present in rat kidney brush border membranes

Localization of a calcium-stimulated ATPase in the basal-lateral plasma membranes of the proximal tubule of rat kidney cortex

In the proximal tubule of the kidney, calcium is reabsorbed by an active transport mechanism. Recently, a Ca2+-activated ATP-phosphohydrolase has been described in plasma membranes from rat kidney cortex, which is different from the Ca2+-ATPase present in mitochondria. To elucidate the role of this enzyme in transepithelial calcium transport we studied its localization within the cell of the proximal tubule. For this purpose, a plasma membrane fraction was subdivided by preparative free flow electrophoresis and the distribution of alkaline phosphatase (brush border microvillus membranes) and Na+−K+-ATPase (basal-lateral plasma membranes) was compared with that of Ca2+-ATPase. The distribution pattern obtained and the corresponding enrichment factors show that a nonmitochondrial Ca2+-ATPase is-in analogy to the Na+−K+-ATPase-located only in the basal-lateral plasma membranes of the proximal tubule. Regarding the different substrate specificity and the insensitivity of the enzyme towards sodium, potassium and ouabain it seems to be possible to differentiate between the two enzymes at a molecular level. It is proposed that the Ca2+-stimulated ATPase is involved in the active transtubular transport of calcium