The proteolysis of immunoglobulin G with long-acting thyroid-stimulating activity

1. Proteolysis of immunoglobulin G with long-acting thyroid-stimulating activity with papain and pepsin shortened the duration of thyroid stimulation in mice prepared for the McKenzie (1958) bioassay. The time-course appeared to be related to molecular size. 2. The activity after proteolysis was recovered solely in the electrophoretically slow F(ab)-fragment. 3. There was no immunological cross-reaction between pituitary thyroid-stimulating hormone and the active fragments of the long-acting thyroid stimulator despite their similar behaviour in the bioassay. 4. The implications of these findings are discussed.     

The food of a community of East African freshwater fishes

Quantitative data on the food of the fishes inhabiting Lake Mcllwaine, Rhodesia, show that the feeding of the dominant species in this community ( Clarias gariepinus (Burchell), Hydrocynus vittatus (Castelnau), Tilapia melanopleura Dumeril, Tilapia mossamhica Peters, Tilapia macrochir Boulenger, Labeo altivelis Peters, and Gnathonemus macrolepidotus (Peters)) covers a wide spectrum, and almost all elements of the potential food supply are utilized. Exceptions are noted, however, and the introduction of the Indian carp, Catla catla (Cuv. & Val.), is advocated in order to utilize the large blooms of phyto- and zooplankton. The oligochaete, Branchiura cf. sowerbyi , which forms over 50% of the benthic biomass is also not utilized as a source of fish food. However, no fish species is known to feed on oligochaetes to any large extent. Predation by the Tigerfish, Hydrocynus vittatus , is shown to have severe effects upon recruitment to the valuable Tilapia fishery, and the reduction of the abundance of H. vittatus by means of selective fishing techniques is advocated.     

The food of a community of East African freshwater fishes

Quantitative data on the food of the fishes inhabiting Lake Mcllwaine, Rhodesia, show that the feeding of the dominant species in this community ( Clarias gariepinus (Burchell), Hydrocynus vittatus (Castelnau), Tilapia melanopleura Dumeril, Tilapia mossamhica Peters, Tilapia macrochir Boulenger, Labeo altivelis Peters, and Gnathonemus macrolepidotus (Peters)) covers a wide spectrum, and almost all elements of the potential food supplyare utilized. Exceptions are noted, however, and the introduction of the Indian carp, Catla catla (Cuv. & Val.), is advocated in order to utilize the large blooms of phyto- and zooplankton. The oligochaete, Branchiura cf. sowerbyi , which forms over 50% of the benthic biomass is also not utilized as a source of fish food. However, no fish species is known tofeed on oligochaetes to any large extent. Predation by the Tigerfish, Hydrocynus vittatus , is shown to have severe effects upon recruitment to the valuable Tilapia fishery, and the reduction of the abundance of H. vittatus by means of selective fishing techniques is advocated.     

Pulsed-field gel analysis of human immunoglobulin heavy-chain constant region gene deletions reveals the extent of unmapped regions within the locus

The human immunoglobulin heavy-chain constant region gene locus is organized in three main gene groups, the physical distances of which are unknown. Different types of gene deletions, originated by unequal crossingover, have been found to encompass one or more genes in the locus. We have analyzed some of these deletions by means of pulsed-field gel electrophoresis, which allows resolution of large DNA fragments. By identifying a fragment containing two of the main gene groups and by observing the size reduction of this fragment in subjects with deletions, we were able to estimate the distance between the two groups and better locate the pseudogene in-between.     

Oestrogens down-regulate type I but not type II adrenal corticoid receptors in rat anterior pituitary

We have studied type I and type II adrenal cortical steroid receptors in the anterior (AL), intermediate (IL) and posterior (PL) lobes of the pituitary and in the hippocampus of ovariectomized-adrenalectomized female rats and in castrated-adrenalectomized male animals, with or without oestrogen treatment. Using [3H]dexamethasone as ligand and conditions suitable for determination of its binding to type I and type II receptors, we found that 4 or 15 days of oestrogen reduced type I receptors in AL by 50-60% without changes in IL, PL or hippocampus, or in type II sites in any of the four neuroendocrine tissues studied. This down-regulatory effect was seen only in female rats and no change was found for males. The reduction in type I sites in AL in oestrogenized female rats was confirmed by labelling type I sites with the synthetic antimineralocorticoid [3H]ZK 91587. Saturation analysis with [3H]ZK 91587 demonstrated that the reduction was due to a reduction in Bmax without change in Kd. We conclude that: (a) type I receptors in the anterior pituitary are under oestrogenic control; (b) there is a sex difference in the response to oestrogen of AL type I sites; and (c) this demonstration may be useful in determining the role of type I receptors in neuroendocrine regulation of the anterior pituitary by hormones derived from the adrenal cortex, and the participation of sex hormones in this process.     

Internal desynchronization of circadian rhythms and tolerance of shift work

Fifteen male subjects including 12 shift workers (oil refinery operators) volunteered to document circadian rhythms in sleep-wake, grip strength of both hands, peak expiratory flow, heart rate, self-rated drowsiness, fatigue and attention. Each of these variables was measured 4 to 6 times/day for 2 to 3 weeks. In addition, both axillary temperature (with a shielded probe) and wrist activity were almost continuously recorded at 15 min intervals during the same time span. Individual time series were analyzed according to several statistical methods (power spectrum, cosinor, chi 2, etc.), in order to estimate the prominent circadian period tau and to evaluate both individual and subgroup differences with regard to tolerance of shift work, age, duration of shift work. The present study confirms for continuously recorded temperature and wrist activity, grip strength of both hands, heart rate and peak expiratory flow that intolerance of shift work is frequently associated with an internal desynchronization. However, this conclusion cannot be extended to circadian rhythms in self-rated drowsiness, fatigue and attention. The internal desynchronization among several circadian rhythms supports the hypothesis that these latter are driven by several oscillators, with presumable differences between right and left hemispheres as suggested by unequal values of tau in rhythms of both hand grip strength. Since an internal desynchronization can be observed in tolerant shift workers having no complaint, it is likely that symptoms of intolerance are related to the subject's sensitivity to internal desynchronization rather than to the desynchronization itself.