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Stage-Dependent Accumulation of Cadmium: RESULTS(1)

RESULTS(1)

Tissue Staging (Fig. 1)

Fluorescence confocal imaging of AO-stained sections verified staging of dissected tissues. As shown in Figure 1, A-E, stage of development of spermatocysts was identifiable by cyst diameter; the presence or absence of a lumen; and the approximate number, ratio, and relative position of germ cell vs. Sertoli cell nuclei. All spermatocysts at a given distance from GZ were in the same stage of development. Dissected regions designated PrM were most heterogeneous, as there are 13 spermatogonial generations in Squalus. birth control yasmin

Elimination of 109Cd from the Peripheral Circulation (Fig. 2; Table 1)

Within 1 h of an i.v. injection of a single tracer dose of 109Cd, radioactivity recovered in the peripheral blood was 31% of the injected dose, and levels decreased progressively thereafter to 4% of the injected dose by Day 7 (Table 1). Elimination curves for blood and plasma were biphasic and, when plotted as log concentration vs. time, indicated two components: a fast component with a half-time of 3.2 h in blood and 1.6 h in plasma, and a slow component with half-times of 150 h and 50 h in blood and plasma, respectively (Fig. 2). Initially (1 h postinjection), the blood: plasma ratio was < 1.0, indicating that the majority of tracer was in the fluid compartment; however, 6 h and 7 days after injection, the blood:plasma ratio had increased to 3:1 and 24:1, respectively, indicating tracer retention in the cellular compartment.
Fig1Stage-Dependent Accumulation
FIG. 1. Organization of spermatogenesis and stages of spermatocyst development in shark testis. The diagrammatic cross section shows the simple diametric progression of spermatogenesis and demarcation of dissected tissues: GZ, PrM, M, PoM (see text). ZD, with a band of apoptotic cysts reflecting the preceding winter’s period of spermatogenic inactivity, appears between PrM and M zones in May/June and was excluded from analyses except where indicated. The EO, a lymphomyeloid tissue, encapsulates the testes at the mature pole. Fluorescence confocal images show spermatocysts representative of staged tissues after staining with AO and their approximate position in the developmental progression: A) GZ with a nest of primitive cysts containing gonocytes (Go); B) PrM zone with cyst containing immature spermatogonia (Sg); C) PrM zone with cyst containing mature Sg; D) M zone with cyst containing spermatocytes (Sc); and E) segment of PoM cyst containing bundles of mature spermatids (St), with heads pointed peripherally and tails projecting into the lumen. Sertoli cell (SC) nuclei are not readily evident in D but are approximately equivalent in number to germ cells in A and B, located adluminally at the stage of maturation shown in C, and are adjacent to the basement membrane in E.

Fig2Stage-Dependent Accumulation
FIG. 2. Blood and plasma elimination of 109Cd. Blood was sampled 1, 3, 6, 12, and 24 h after 109Cd injection, and animals were killed at the 24-h time point for tissue analysis (n = 3). Additional samples were taken from animals killed 3 and 7 days after tracer injection (n = 3 each). Samples were assayed in triplicate. Values are the mean and SEM of 3 animals. Biphasic curves were transformed to linear plots and t1/2 was calculated as the time taken to reach 50% of the time zero value.

TABLE 1. Organ weights and body distribution (% bw = % body weight) of 109Cd in male dogfish shark (Squalus acanthias) 1, 3, and 7 days after tracer administration, and effects of Cd pretreatment.

Organ 1-Day retention3 3-Day retention8 7-Day retentiona 3-Day pretreatedb 1-Day retention 7-Day pretreatedb 1-Day retention
Weight (% bw) 109Cd (% dose) Weight (% bw) 109Cd (% dose) Weight (% bw) 109Cd (% dose) Weight (% bw) 109Cd (% dose) Weight (% bw) 109Cd (% dose)
Kidney 0.48 5.62 0.35 3.45 0.43 4.47 0.40 3.03 0.41 3.46
±0.12 ±1.62 ±0.35 ±1.05 ±0.03 ±1.11 ±0.10 ±0.99 ±0.05 ±0.50
Liver 9.33 37.15 10.48 25.58 10.95 26.80 9.63 17.80 10.70 21.98
±0.97 ±5.78 ±0.45 ±1.95 ±1.29 ±6.89 ±3.30 ±4.33 ±2.17 ±1.19
Spleen 0.45 1.62 0.42 1.56 0.40 1.89 0.32 0.69 0.35 0.58
±0.10 ±0.41 ±0.06 ±0.53 ±0.02 ±0.83 ±0.08 ±0.23 ±0.07 ±0.09
Heart 0.12 0.32 0.14 0.36 0.14 0.38 0.12 0.35 0.14 0.41
±0.01 ±0.05 ±0.01 ±0.05 ±0.02 ±0.07 ±0.01 ±0.11 ±0.01 ±0.15
Rectal gland 0.07 0.12 0.08 0.16 0.08 0.13 0.07 0.09 0.07 0.11
±0.02 ±0.04 ±0.01 ±0.05 ±0.00 ±0.03 ±0.01 ±0.01 ±0.01 ±0.01
Brain 0.09 0.02 0.11 0.02 0.13 0.02 0.08 0.01 0.08 0.01
±0.02 ±0.00 ±0.02 ±0.00 ±0.02 ±0.01 ±0.00 ±0.00 ±0.01 ±0.00
Skeletal muscle c 10.59 c 5.85 c 5.89 c 6.31 c 8.59
±0.40 ±2.12 ±1.56 ±1.48 ±4.17
Whole blood d 11.55 d 6.55 d 4.39 d 10.57 d 8.37
±2.06 ±3.43 ±2.16 ±2.67 ±0.80
Plasma d 2.96 d 1.21 d 0.15e d 8.80e d 7.65e
±0.20 ±0.71 ±0.05 ±3.14 ±0.76
Testis 1.93 0.87 1.60 0.88 1.56 0.98 1.85 0.54 1.71 0.49
±0.12 ±0.08 ±0.25 ±0.20 ±0.22 ±0.17 ±0.25 ±0.10 ±0.16 ±0.08
Dose recovered (%) 68 ± 16 45 ±5 45 ±3 40 ±9 45 ±4
Body weight (g) 1640 ± 250 1181 ± 186e 1393 ± 108e 192 7 ± 241 1857 ± 101
Snout-vent (cm) 46 ±3 40 ±3 41 ±1 46 ±3 45 ±2

a Animals received a single i.v. injection of 109Cd (2.8 ^Ci) 1, 3, or 7 days before killing.
b Animals received a single i.v. injection of CdCl2 (5 mg/kg) 3 or 7 days and a tracer dose of 109Cd 24 h before killing. c Skeletal muscle was empirically determined at 75% of body weight.
d Blood volume was estimated at 6.8% and plasma at 5.5% of body weight (see Materials and Methods). e Indicates difference when compared to Day 1 control (p < 0.05).