Studies on chiasma frequency and distribution in two fertile men carrying reciprocal translocations; one with a t(9;10) karyotype and one with a t(Y;10) karyotype

Summary The frequency and distribution of chiasmata was investigated in two fertile carriers of reciprocal translocations, one with a 46,XY,t(9;10)(p22;q24) karyotype and one with a 46,X,-Y,+der(Y),t(Y;10)(q12;q24) karyotype. In both cases the chromosomes involved in the translocation showed an increase in chiasma frequency in comparison to karyotypically normal controls and in both cases this increase was localised, affecting only one interstitial segment of each translocation quadrivalent. In the t(9;10) case chiasmata appeared in substantial numbers in a novel location, the proximal two thirds of 9p, while in the t(Y;10) case chiasmata appeared in a conventional location, the medial region of 10q, but at an increased frequency. Furthermore there was evidence for inter-chromosomal effects in the t(9;10) case.     

Site-specific integration of an F'' lac pro factor in the region of the replication origin (oriC) of E. coli

Summary An episome, F 128, which carries approximately 8x10⁴ base pairs of chromosomal DNA homologous to the lac pro region of the E. coli chromosome, has been found to integrate into the oriC region of the chromosome in a site specific reaction. While the event appears to be recA-dependent, no homology between the episome and this region of the chromosome was detected. The Hfr strains formed result from the integration of intact F 128 molecules. The structure of the Hfr strains generated has been determined and their transfer properties analyzed.     

Versatility and specialization in labrid fishes: ecomorphological implications

Summary The term specialized has been used to describe species that possess unique functional attributes and/or a narrow, stereotyped range of attributes, but there are few comparative functional analyses of specialists and generalists. If species with functional morphological specializations are capable of functioning over a broad range, the link between morphology and ecology may be relaxed under certain environmental conditions. In this study, high-speed films of jaw movements during prey capture were compared statistically for three coexisting coral reef fish species in the family Labridae, one trophic specialist and two trophic generalists. The trophic specialist possessed a unique functional feature related to the movement of the hyoid in the floor of the mouth, while the trophic generalists were not observed to possess any functional specializations. All three species showed functional versatility in that they were able to adjust their prey capture mechanism in response to the evasive potential of the prey. The functional versatility of trophic specialists has implications for ecomorphological studies, since species characterized as possessing unique functional or morphological features may demonstrate marked flexibility in ecological variables such as diet or foraging behavior, decreasing the likelihood of identifying correlations between morphology and ecology.     

Variation of cooling rate and concentration of dimethyl sulfoxide on rabbit kidney function

Rabbit kidney function was assessed in vitro after cryoprotection with either 3 or 4 M dimethyl sulfoxide. The introduction and removal of the cryoprotectant was carried out in a stepwise progressive manner and the removal in a stepwise progressive manner with hypertonic mannitol solutions. This in vitro model can be shown to respond to various ischemic-like states resulting in poor or absent function. Active tubular transport can be demonstrated. It has been used by many authors as an intermediate step prior to the ultimate test of reimplant and contralateral nephrectomy. Variations in the rate of cooling at cryoprotection levels of 3 and 4 M dimethyl sulfoxide concentration (Me2SO) were carried out. In general, at 3 M concentration of Me2SO, creatinine clearance, sodium and glucose reabsorption are preserved with a fair degree of success after cooling to -10, -15, and -20 degrees C in our model, when the rate of cooling to these levels is 1.0 degree C/min. When a cooling rate of 0.5 degree C/min is used, renal function is significantly reduced whether the final temperature is -10, -15, or -20 degrees C. Control rabbit kidneys will tolerate 4 M concentration of Me2SO and give fairly good function. When cooled to -15 or -20 degrees C, there is poor function at 0.1 and 0.5 degrees C/min. Fair function is obtained at the rate of 1 degree C/min to -10 degrees C. Therefore, at cryoprotectant levels of 3 and 4 M Me2SO, kidney function as assayed by in vitro perfusion, is better when the cooling rate is 1.0 degree C/min.