The First Cells Ascend

Central/Tertiary structures The fish olfactory bulb is a fourlayered structure much as in higher vertebrates. Within the 2nd layer, the first synapse for olfactory input is on the dendrites of the mitral cells (MC). About 1000 ORN axons converge on one MC, a ratio similar to mammals. The MC output, from cells at various levels, leads into several glomeruli and receives (inhibitory) input from granule cells. The latter also innervate a distinct cell type in the MC layer of teleosts — the ruffed cells (RC), with which they have reciprocal synapses [Fig. 2.18(a)] both relay cells send ascending fibres to forebrain centres (Kosaka and Hama, 1982). The RC are unlike the MC since they are not stimulated by the ORNs directly. Their interactions (Chap. 5) may contribute to the processing of pheromonal stimuli (Zippel, 2000). The main bulbar pathways project to several nuclei in the forebrain via two ipsilateral tracts, the lateral and medial [Fig. 2.18(b)], the latter mediates sexual behaviour and the former probably other behaviours (Hara,... 

The intracellular negative electrical potential opposes chloride entry into cells. In the early proximal tubule the main cation, sodium, is predominantly reabsorbed concomitantly with bicarbonate so that the luminal chloride concentration actually increases. There are two main reabsorption mechanisms for chloride. The first is via an antipoiter in exchange for secretion of other anions (e.g., bicarbonate) or formate. The second occurs in the final two thirds of the proximal tubule. In the thick ascending limb of the loop of Henle, chloride is reabsorbed in association with sodium via NKCC2. The concentration gradient is maintained by a basolateral chloride pump, CLC-Kb (see Figure 45-7). A further chloride channel, CLC-5, is expressed at multiple sites in the nephron. ... 

As first shown by Escobar et al. (1986) in the neocortex of the mouse, the apical dendrites of the pyramidal cells in layer 6a do not join the clusters formed by the apical dendrites of the pyramidal cells in layers 5-2. Instead they form their own independent groupings, which we have referred to as bundles. Since the pyramidal cells of layer 6a are small, their apical dendrites are thinner than those of the pyramidal cells in upper layers and they form numerous bundles that ascend as far as layer 4, where they terminate and form their apical tufts (see Figs. 3 and 4). 

In contrast to serum, urine can fluctuate dramatically in protein and salt concentrations, and both the inter- and intra-patient variability can be quite large. Typically, the urine samples containing the highest protein concentrations are first and second morning void samples. To minimize the impact of this variability in the clinical setting, samples are often collected over the course of 24 h (8). Urine from normal individuals has low protein concentrations (150 mg/day). Approximately 10% of this protein is albumin the remaining proteins are various serum proteins as well some that arise from the renal cells themselves (9). Fifty percent of the protein is the Tamm-Horsfall mucoprotein (96 kDa), which is secreted by cells of the ascending limb of the loop of Henle (10). 

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