Testicular Germ Cell Tumors (TGCTs) are the most common malignancy in young men. However, there are few in vivo animal models that have been developed to study this disease. We have used the pufferfish (fugu) lymphocyte-specific protein tyrosine kinase (flck) promoter, which has been shown to enforce high-level expression in the testes of transgenic mice, to express Simian Virus 40 Large T (SV40 T) antigen in zebrafish testes. Zebrafish that express T antigen (TAg) develop TGCTs after a long latency of more than one year. Although overt TGCTs are only evident in 20% of the fish, occult TGCTs can be detected in 90% of the transgenic fish by 36 month of age. The TGCTs resemble the human disease in terms of morphology, gene expression pattern, and can be transplanted to healthy wild-type recipient fish. In addition, enforced expression of the zebrafish the stem cell leukemia (scl) gene in the zebrafish testes also generated TGCTs in transgenic fish. These results demonstrate the feasibility of studying TGCTs in a model organism.

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This paper was prepared for the Abnormal Subsurface Pressure Symposium of the Society of Petroleum Engineers of AIME, to be held in Baton Route, La., May 15–16, 1972. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon requested to the Editor PETROLEUM ENGINEERS JOURNAL is usually granted upon requested to the Editor of the appropriate journal, provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers Office. Such discussions may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines. Abstract While sands and permeable-carbonate reservoirs once served as a convenient source of pressure measurements—and of some erroneous concepts of pressure "graients" as well—we now realize that most fluid pressures originate in the relatively-impermeable clays and shales from whence they are transmitted to the sands and carbonates, where they tend to gradually bleed off and reach "hydrostatic" equilibrium. The water being released dynamically, continuously, and currently from the younger shales (Tertiary and into Cretaceous), during their compaction and diagenesis, appears to be primarily responsible for the generation of overpressures. This shale-pressuring follows no consistently "linear" gradient, showing many irregularities and pressure "reversals"—thereby causing, and pressure "reversals"—thereby causing, and explaining, many of oar complex drilling problems. problems. Since shales—quite thick in comparison to the relatively thin sands-are the predominant "rock" in most of our predominant "rock" in most of our sedimentary basins, their water content becomes a tremendous hydrodynamic reservoir for fluid pressures, and perhaps the origin of the pressures, and perhaps the origin of the very hydrocarbons for which we are drilling The diagenetic changes in shale mineralogy which accompany the release and subsequent movement of internal water from shales are being utilized worldwide in a convenient and reliable group of parameters for monitoring pressure changes (either up or down) from shale cuttings while drilling is in progress. When these shale mineralogy parameters are properly interted (to allow for such things as "jump shifts" in geologic age caused by folding and faulting; missing sediments; or for 11 strange" minerals squirted spasmodically by volcanic activity into the depositing shale sediments), they tend to fit the preceding generalizations and verify dynamic preceding generalizations and verify dynamic considerations of overpressuring. Four such case histories are presented here. Introduction Dynamic mechanisms of pressure generation are not new to this group*, having been discussed in prior symposia by Jones, Burst and several others.

Each year, a painfully significant number of drilling wells experience baffling, virtually insurmountable, prohibitively expensive pressure imbalance problems – losing mud while circulating; but gaining during trips – not explainable as simple overbalance/underbalance. Every one of these wells seems to require as much as 17.5-18.5 ppg mud weight, and still seems on the verge of blowing out --- but. never quite does. Pressure balance indicators are in puzzling conflict. Most of the drilling parameters indicate continued underbalance, even after – especially after – mud weights have been escalated farbeyond the natural pore pressures of, say, 16.0 ppg (as determined by well-log pressure plots and confirmed by the offset wells that have been drilled, relatively trouble-free, at the lesser mud density). The borehole apparently balloons or breathes, slightly, when long sections of already-overpressured, wet, plastic shales are drilled this greatly in overbalance (but not by then easily recognisable as overbalance); taking 20-30 bbls of mud while circulating and giving it back (if we let it) when pumps are shut down. This new, superimposed and "bottled-up" hydrostatic pressure in the wellbore from the (excessive) mud density is then very real. When we push on the (16.0 ppg) shale/water mixture of the formation with 17.5 ppg mud (13,000 psi --- 1500 psi of overbalance); it can yield only slightly within its confines (the water component being virtually incompressible) before it "pressures up" and pushes right back with that same force. We have created in the shale body a super-natural, self-induced pore pressure greater than its original, natural pore pressure. We have "charged" the shale. Several well histories – and their "natural" pore pressure plots from well logs – are presented here, to illustrate that these impossibly delicate pressure-balance situations of our own doing can and do develop; how they can be recognized by their characteristic symptoms; and how they can be corrected, or simply avoided in the first place.