Primary structure analysis proves that protein phosphatases 2C1 and 2C2 are isozymes

The two recently discovered forms of protein phosphatase 2C, termed 2C1 and 2C2, were digested with CNBr or trypsin, and several peptides corresponding to two regions of the protein were sequenced. These studies revealed close homology between the two enzymes with 49 identities over the 62 residues that could be compared directly. The results establish that protein phosphatases 2C1 and 2C2 are the products of different genes. The C-terminus of protein phosphatase 2C2 has also been identified.     

Natural Selection and Y-Linked Polymorphism

Several population genetic models allowing natural selection to act on Y-linked polymorphism are examined. The first incorporates pleiotropic effects of a Y-linked locus, such that viability, segregation distortion, fecundity and sexual selection can all be determined by one locus. It is shown that no set of selection parameters can maintain a stable Y-linked polymorphism. Interaction with the X chromosome is allowed in the next model, with viabilities determined by both X- and Y-linked factors. This model allows four fixation equilibria, two equilibria with X polymorphism and a unique point with both X- and Y-linked polymorphism. Stability analysis shows that the complete polymorphism is never stable. When X- and Y-linked loci influence meiotic drive, it is possible to have all fixation equilibria simultaneously unstable, and yet there is no stable interior equilibrium. Only when viability and meiotic drive are jointly affected by both X- and Y-linked genes can a Y-linked polymorphism be maintained. Unusual dynamics, including stable limit cycles, are generated by this model. Numerical simulations show that only a very small portion of the parameter space admits Y polymorphism, a result that is relevant to the interpretation of levels of Y-DNA sequence variation in natural populations.     

Molecular cloning of cDNA for human prostatic acid phosphatase

A human liver cDNA library in λgt11 was screened with polyclonal antiserum to human acid phosphatase isoenzyme 2a/4. About eleven positive clones have been obtained. Two clones, λ Hap21 and λ Hap22 were further characterized: clone λHap21 contained a 0.8-kb cDNA insert and clone λHap22 a 1.8–2.0-kb insert. XbaI digestion of λHap22 generated two fragments of 1.0 and 0.9 kb. BglII digestion resulted in a 1.2-kb fragment and several smaller fragments of undetermined size. Clone 1 Hap22 contained all the genes carried by λ gt11(lac 5cI857nin 5Sam 100) and the 2-kb insert. An Escherichia coli(λHap22) lysogen was generated, and its acid phosphatase activity was approximately ten-fold higher than that in the control nonlysogenic lysate. Western-blot analysis of total proteins present in this E. coli(λHap22) lysate revealed that the non-induced λHap22 prophage directed the synthesis of an approx. 175-kDa protein. This protein was recognized by antibody to the human acid phosphatase isoenzyme 2a/4 and anti-β-galactosidase and was produced only upon induction with IPTG. These results indicated that AHap22 carried a major portion of the gene coding for the human acid phosphatase isoenzyme 2a and/or 4 and this protein fragment of acid phosphatase was sufficient to manifest enzymatic activity.     

The effect of pancreatic mesenchyme on the differentiation of endocrine cells from gastric endoderm

To determine whether mesenchyme plays a part in the differentiation of gut endocrine cells, proventricular endoderm from 4- to 5-day chick or quail embryos was associated with mesenchyme from the dorsal pancreatic bud of chick embryos of the same age. The combinations were grown on the chorioallantoic membranes of host chick embryos until they reached a total incubation age of 21 days. Proventricular or pancreatic endoderm of the appropriate age and species reassociated with its own mesenchyme provided the controls. Morphogenesis in the experimental grafts corresponded closely to that in proventricular controls, i.e. the pancreatic mesenchyme supported the development of proventricular glands from proventricular endoderm. Insulin, glucagon and somatostatin cells and cells with pancreatic polypeptide-like immunoreactivity differentiated in the pancreatic controls. The latter three endocrine cell types, together with neurotensin and bombesin/gastrin-releasing polypeptide (GRP) cells, developed in proventricular controls and experimental grafts. The proportions of the major types common to proventriculus and pancreas (somatostatin and glucagon cells) were in general similar when experimental grafts were compared with proventricular controls but different when experimental and pancreatic control grafts were compared. Hence pancreatic mesenchyme did not materially affect the proportions of these three cell types in experimental grafts, induced no specific pancreatic (insulin) cell type and allowed the differentiation of the characteristic proventricular endocrine cell types, neurotensin and bombesin/GRP cells. However, an important finding was a significant reduction in the proportion of bombesin/GRP cells, attributable in part to a decrease in their number and in part to an increase in the numbers of endocrine cells of the other types. This indicates that mesenchyme may well play a part in determining the regional specificity of populations of gut endocrine cells.     

Fracture toughness of horns and a reinterpretation of the horning behaviour of bovids

The keratinous horns of bovids are used in intraspecific combat to gain access to females in oestrus. Horn sheath keratin is a composite material consisting of stiff protein fibres and a pliant protein matrix. Unlike antlers, horns are permanent structures which are likely to accumulate damage during fighting. Therefore, horn sheath keratin should be resistant to fracture (tough) and insensitive to surface defects (scratches and cracks) which may weaken horns by acting as stress concentrators.
The effect of water on the toughness and notch-sensitivity of horn sheath keratin was investigated in three-point bending and tensile tests. Several measures of toughness were made on dry (0% water content), fresh (20%) and wet (40%) horn keratin, including total work of fracture, Gurney & Hunt work of fracture, critical strain energy release rate and critical stress intensity factor.
The mean total work of fracture of fresh horn is about 40 kJ/m² which is relatively much greater than most biological and synthetic materials. Most of the work of fracture is due to plastic yielding of the matrix (50–75%); the rest is due to crack-tip specific fracture mechanisms such as fibre pull-out and Cook Gordon crack-stopping. Dehydration reduces the total work of fracture of horn keratin by preventing the yielding of the matrix.
The strength of fresh and wet horn is insensitive to notches, but dry horn is very notch-sensitive. Therefore, bovids must avoid dehydration of their horns due to the desiccating effect of the environment. The 'horning' behaviour of bovids may be a maintenance activity which ensures that the horn sheath is adequately hydrated to remain tough and notch-insensitive.     

Doppler studies in the growth retarded fetus and prediction of neonatal necrotising enterocolitis,haemorrhage, and neonatal morbidity.

In 82 consecutive cases of intrauterine growth retardation managed by established criteria fetal Doppler studies identified 29 fetuses with absence of end diastolic frequencies in the fetal aorta. These same fetuses were significantly more growth retarded (p less than 0.001) and had an earlier gestational age at delivery (p less than 0.001) than those with end diastolic frequencies present. A subgroup of these cases was analysed in more detail to examine the prognostic value of this phenomenon for the neonate. Two groups of neonates of equivalent gestational age and with a birth weight below 2000 g were compared. There were 26 neonates with absent end diastolic frequencies (group 1) and 20 with end diastolic frequencies (group 2) in the fetal aorta. Those in group 1 were more likely to suffer perinatal death (p less than 0.05), necrotising enterocolitis (p less than 0.01), and haemorrhage (p less than 0.05). Only 4 (15%) of the babies in group 1 had an uncomplicated neonatal period compared with 15 (75%) in group 2 (p less than 0.001). The circulatory changes identified in these cases may provide a more sensitive measure of critical fetal compromise than current techniques and thus allow the clinician to deliver the fetus before irreversible tissue damage has occurred.