Effect of increased distal sodium delivery on organic osmolytes and cell electrolytes in the renal outer medulla

Sodium absorption in distal tubule segments was stimulated by increasing the distal delivery via infusion of hypertonic saline. In these animals, and in control rats, electrolyte concentrations in thick ascending limb cells, light and dark cells of the collecting duct in the outer and inner stripe of the outer medulla and in cells of the proximal straight tubule (outer stripe only) were studied. The measurements were performed by electron microprobe analysis of freeze-dried cryosections of the outer medulla. In addition, organic osmolytes (glycerophosphorylcholine, betaine and myo-inositol) were measured by high performance liquid chromatography in cortex and outer medulla. Augmented delivery of sodium chloride to the distal tubule was associated with increased sodium concentrations of thick ascending limb cells both in the outer and inner stripe and of medullary collecting duct light and dark cells in the outer stripe. While the sum of organic osmolyte concentrations was 28% higher in the outer medulla of the salt-loaded animals compared with controls, this value was unchanged in the renal cortex. These findings indicate that the primary event underlying stimulation of sodium absorption along the thick ascending limb during increased distal sodium delivery is enhanced entry of sodium across the apical cell membrane. This would be expected to lead to higher cell sodium concentrations and stimulation of basolateral active Na-K-exchange. The enhanced transport activity of outer medullary tubules may be associated with increased interstitial tonicities and intracellular retention of organic osmolytes.     

The early phase of experimental acute renal failure

Summary Experiments were designed to determine whether leakage of substances across the tubular epithelium, which are impermeant in the normal kidney, falsifies the measurement of glomerular filtration rate in acute renal failure. Permeability to those substances most commonly used for filtration rate determination, polyfructosan, inulin and ferrocyanide, was estimated by measuring their recoveries following perfusion through various nephron segments in haeme pigment, ischaemic and nephrotoxic models of actue renal failure. Late proximal recovery of¹⁴C ferrocyanide was only marginally decreased compared to controls, by a maximum of 6%. Distal recovery of polyfructosan,¹⁴C and³H inulin were depressed somewhat more, by a maximum of 11%. Urinary recovery of¹⁴C inulin was reduced by only 15% in kidneys showing severely restricted renal function. It is concluded that tubular leakage is not a feature of significance in the early phase of moderate acute renal failure, that ferrocyanide and inulin are reliable markers for the determination of nephron filtration rate and water reabsorption, and that the reduction in whole kidney inulin or polyfructosan clearance reflects primarily a reduction in glomerular filtration rate.     

Neither lymphotoxin alpha nor lymphotoxin beta receptor expression is required for biogenesis of lymphoid aggregates or differentiation of natural killer cells in the pregnant mouse uterus

Gene ablation studies in mice indicate that lymphotoxin (LT)alpha, LTbeta and LTbetaR are essential for the genesis of lymph nodes (LN), normal structural development of peripheral lymphoid tissues and the differentiation of natural killer (NK) cells. LTbetaR binds to the heterotrimeric cytokines LTalpha1beta2 and LIGHT. LTs also regulate stromal cell expression of lymphocyte homing chemokines. Uterine decidualization in normal (+/+) mice is accompanied by the appearance and maturation of large numbers of uterine NK (uNK) cells that differentiate from precursors mobilized to the uterus from secondary lymphoid tissues. uNK cells accumulate in a transient, lymphocyte-rich region known as the metrial gland or, more recently, the mesometrial lymphoid aggregrate of pregnancy (MLAp). To determine if LTs contribute to development of the MLAp, and to the differentiation and/or localization of uNK cells, a histological study was undertaken of implantation sites from LTalpha null, LTbetaR null and gestation day-matched, normal mice. Implantation sites from the gene-ablated mice contained abundant numbers of uNK cells that localized appropriately. This indicates that the stromally derived molecules supporting NK cell differentiation in the uterus differ from those used in secondary lymphoid organs.     

Limb anomalies: Developmental and evolutionary aspects

In this review we describe the developmental mechanisms involved in the making of a limb, by focusing on the nature and types of interactions of the molecules that play a part in the regulation of limb patterning and characterizing clinical conditions that are known to result from the abnormal function of these molecules. The latter subject is divided into sections dealing with syndromal and nonsyndromal deficiencies, polydactylies, and brachydactylies. Conditions caused by mutations in homeobox genes and fibroblast growth factors and their receptor genes are listed separately. Since the process of limb development has been conserved for more than 300 millions years, with all the necessary adaptive modifications occurring throughout evolution, we also take into consideration the evolutionary aspects of limb development in terms of genetic repertoire, molecular pathways, and morphogenetic events.     

Endoreduplication in conjunction with tumor progression in an aneuploid laryngeal squamous cell carcinoma

We report the case of a 58-year-old man who presented with a squamous cell carcinoma pT1a G2 of the left vocal cord. Six months after histologically verified complete resection, the patient experienced an endolaryngeal and extralaryngeal local recurrence pT4 pN2b G2. We applied DNA flow cytometry (FCM) and comparative genomic hybridization (CGH) on both primary and recurrent tumor. The primary tumor and the endolaryngeal compartment of the relapse was an aneuploid cell clone with a FCM DNA index of 1.42 and 1.44, respectively. The extralaryngeal compartment showed a shift featuring a DNA index of 2.78. In the primary tumor and in both compartments of the recurrence there was an identical pattern of complex chromosomal imbalances as detected in CGH (CGH karyotype: rev ish enh [8q24.2-q24.3, 10q26.1-q26.3, 11q24-q25, 12q24.2-q23.33,X], dim [4q, 13q14.3-q31], amp[1p36.1-p36.2]). Hence, the recurrence was not associated with further gains and losses of chromosomal material. However, in the anterior part of the recurrence, the aneuploid tumor cell genome had completely doubled, obviously due to endoreduplication. Immunohistochemical analysis of several cell-cycle regulators revealed altered expression of checkpoint proteins, pointing to a complex disturbance in cell-cycle regulation.     

T-cell variant of classical Hodgkin's lymphoma with nodal and cutaneous manifestations demonstrated by single-cell polymerase chain reaction

The atypical cells of CD30(+) cutaneous lymphoproliferative disorders (CD30CLD) are commonly of T-cell origin and frequently have a similar morphology as Hodgkin or Reed-Sternberg cells of Hodgkin's lymphoma (HL). HL is one of the tumors associated with CD30CLD. Although most studies support a B-cell derivation of the tumor cells in HL, recently a few cases of classical HL with T-cell genotype have been reported. We report a patient who presented with CD30CLD whose lymph nodes showed classical HL of mixed cellularity subtype at presentation. By single-cell PCR, the same clonal gene rearrangements of the T cell receptor-beta gene locus could be assigned to the CD30(+) and CD15(+) cells of both skin and lymph node. In a lymph node biopsy specimen taken in relapse after several courses of chemotherapy, the CD30(+) tumor cells were abundant. The T cell-derived tumor cells displayed aberrant expression of the Pax-5 gene in all specimens. A common clonal origin of both CD30CLD and HL of the lymph node in the patient presented here suggests that HL with T-cell genotype exists in association with CD30CLD as well as in sporadic cases and may share clonal origin with the skin tumor.     

Coreceptor Switch of [MLV(SIVagm)] pseudotype vectors by V3-loop exchange

Retroviral vectors derived from murine leukemia virus (MLV) have been pseudotyped with a variant of the envelope glycoprotein (Env) of nonpathogenic simian immunodeficiency virus from African green monkeys (SIVagm) to result in [MLV(SIVagm-wt)] vector particles. The variant env gene encodes a full-length surface envelope glycoprotein (SU) and a C-terminally truncated transmembrane protein (TM). To change the coreceptor usage of this vector from CCR5 to CXCR4, which is predominant on human CD4-positive lymphocytes, the putative V3-loop of SIVagm SU was replaced by that of the T cell tropic HIV-1 variant BH10. The resulting [MLV(SIVagm-X4)] vectors were shown to specifically transduce CD4/CXCR4-positive cell lines, demonstrating the equivalent function in cell entry and choice of coreceptor usage of the V3-loops of SIVagm and HIV-1. These modified vectors were able to transduce primary human lymphocytes and were resistant to neutralization by sera from HIV-1-infected individuals. The [MLV(SIVagm-X4)] pseudotype vector generated is thus a promising candidate vector, e.g., for in vivo gene therapy of HIV-1 infection.     

Defensin deficiency, intestinal microbes, and the clinical phenotypes of Crohn's disease

Crohn's disease is a chronic, inflammatory disease of the intestinal mucosa. Although intestinal bacteria are implicated in disease pathogenesis, the etiology is still unclear. The main location of disease is the small intestine (ileum) and the colon. Ileal disease has been linked to a mutation in the NOD2 gene. Defensins are antimicrobial peptides and in the ileum, are mainly expressed in Paneth cells, epithelial cells that also express NOD2. In the colon, defensins are expressed by enterocytes or metaplastic Paneth cells. Crohn's disease patients with ileal involvement, compared with controls or Crohn's patients without ileal involvement, have diminished expression of ileal Paneth cell defensins. This decrease is even more pronounced in Crohn's patients displaying a NOD2 mutation. In contrast, Crohn's disease of the colon is characterized by an impaired induction of beta-defensins in enterocytes. The colonic expression of the constitutive beta-defensin 1 is also decreased in the inflamed colonic mucosa, but this decrease is less specific to Crohn's disease, as it can also be found in ulcerative colitis patients. In conclusion, the regional localizations of Crohn's disease, ileal or colonic disease, can be linked to different defensin profiles. Crohn's disease of the ileum is associated with diminished defensin expression in Paneth cells. Crohn's disease of the colon is associated with diminished beta-defensin expression in enterocytes. Thus, it can be speculated that decreased defensin levels lead to a weakened intestinal barrier function to intestinal microbes and might be crucial in the pathophysiology of Crohn's disease.     

Evaluation of Mannitol Salt Agar for Detection of Oxacillin Resistance in Staphylococcus aureus by Disk Diffusion and Agar Screening

Mannitol salt agar was evaluated for detection of oxacillin resistance in 136 Staphylococcus aureus isolates. All mecA-positive isolates (n = 54) were correctly categorized as oxacillin resistant by the disk diffusion test (1-μg disk; zone diameter, <16 mm); the specificity was 97.6%. Agar screening (2 μg of oxacillin per ml) revealed a sensitivity of 98.1% and a specificity of 95.1%.     

The Dominant Epitope of Borrelia garinii Outer Surface Protein C Recognized by Sera from Patients with Neuroborreliosis Has a Surface-Exposed Conserved Structural Motif

Epitope mapping of outer surface protein C (OspC) by using sera from patients with neuroborreliosis led to the identification of one single major immunodominant epitope within the C-terminal 10 amino acid residues. Peptide binding studies and alanine replacement scanning of the C-terminal decapeptide, PVVAESPKKP, revealed a critical role for the PKKP sequence and its terminal carboxyl group for the binding of immunoglobulin M (IgM) antibodies from patients with Lyme borreliosis. Electron microscopy of antibody-labeled spirochetes indicated that the C-terminal region is exposed on the surface of the spirochete. Based on homology to proteins of known function, this region most probably adopts a polyproline II-like helix, which is found in surface-exposed structures involved in protein-protein interactions. This structural motif is highly conserved in Borrelia species causing Lyme borreliosis and subjected to purifying selection. We suggest that the abundance of the C-terminal region of OspC on the surface of B. burgdorferi allows a multimeric high-avidity interaction between the spirochete and surface Igs on B cells. The resulting cross-linking of surface Igs on B cells may induce a T-cell-independent B-cell activation without IgM-to-IgG switching, thus explaining the lack of IgG antibodies to OspC in neuroborreliosis.