Ontogeny of hemoglobins: Evidence for hemoglobin M

A new autosomal codominant hemoglobin mutation alters hemoglobin M of the primitive red cell line and hemoglobin D found in definitive cells. That Hb M and Hb D are altered by the same gene mutation supports the idea that Hb M shares a polypeptide chain with Hb D. It is concluded that in the switch from primitive hemoglobins to those of the definitive type, there are at least two α chains conserved; α^A of Hb E in Hb A and α^D of Hb M in Hb D.     

Human chromosomes. Evidence for autosomal sexual dimorphism.

The karyotypes of 100 males and 100 females, each assembled by the trypsin banding method, are examined in a study designed to investigate sex differences among autosomes. It is shown that female autosomes are consistently longer than those of the males, with respect to both the short and long arm measurements. In addition, discriminant analysis is used to distinguish between the male and female karyotypes. We find that, using autosomal measurements alone, this can be done with a high probability of success.     

Sexual dimorphism in the regulation of meiotic process in the rabbit

Meiosis, mitosis, and apoptosis during fetal and postnatal periods were investigated in order to explore mechanisms of sexual dimorphism in initiation of germ cell meiosis. Gonads were obtained from Japanese white rabbits from 23 to 51 days postcoitum (dpc). Gonadal thin sections were stained with hematoxylin and eosin. Germ cell alkaline phosphatase and apoptosis were detected with histochemical and immunohistochemical methods, respectively. In the ovary, meiotic germ cells were initially recognized at 29 dpc and arrested after enclosure within follicles. Similarly, meiotic germ cells were recognized outside seminiferous tubules at 29 dpc, but no meiotic figures were identified in intratubular spaces. Apoptotic germ cells were not recognized in the intratubular spaces before 35 dpc, and no apoptotic figures were recognized in the ovary during the period studied. In conclusion, the initiation of meiosis in testicular interstitial tissue at the time comparable to that in the ovary indicates that germ cells of both sexes have the ability to enter meiosis during the same stage of fetal development; and it appears most likely that delayed initiation of meiosis in the intratubular space is attributable to meiosis-inhibiting substance(s) present in seminiferous tubules.     

Evidence for somatostatin binding sites in rabbit kidney

Specific binding sites for somatostatin have been identified in cytosolic fraction of rabbit kidney (cortex and outer medulla) using 125I-Tyr11-somatostatin. The binding was saturable and reversible, as well as time and temperature dependent. Optimal pH for binding was observed at about 7.4. Scatchard plots were compatible with the existence of two classes of binding sites: a first class with a high affinity (Kd = 40 nM) and a low binding capacity (2.0 pmol somatostatin/mg protein) and a second class with a low affinity (Kd = 222 nM) and a high binding capacity (114.3 pmol somatostatin/mg protein). Vasoactive intestinal peptide, neurotensin, substance P, Leu-enkephalin and vasopressin had practically no effect on somatostatin binding. The properties of these binding sites strongly support the concept that somatostatin could behave as a regulatory peptide on the rabbit kidney.     

Geminate recombination of CO in rabbit, opossum, and adult hemoglobins

The geminate recombination of CO with Hb following dissociation by a 10-ns laser pulse has been studied as a function of pH (9.2 and 7.0 without inositol hexaphosphate and 6.0 with inositol hexaphosphate) and temperature (5-35 degrees C). The hemoglobins studied included adult, Rothschild, rabbit, opossum, and carp. Despite significant differences in their structural and functional properties, the first four of these hemoglobins show similar trends in the yields, rates, and activation energies of the geminate recombination. The nature of the "cage recombination" in hemoglobin is discussed in the light of such findings. Neither a slow diffusion model nor a model based upon a specific non-heme binding site accounts for the observations.     

Evidence for multiple lipase forms in the rabbit pancreas

Evidence is presented of the existence of at least two forms of lipase (A and B) in homogenized rabbit pancreas. These forms are separated by means of gel filtration and anion-exchange chromatography. Both forms are colipase-dependent, but lipase A is activated to a significant extent by 140 mmol/l NaCl even in the absence of the protein cofactor. Lipase A exhibits greater affinity towards emulsified triolein than does lipase B, as evidenced by the respective apparent Km values. Lipase B appears to be more colipase-dependent and resembles more closely the 'pancreatitis' lipase of human plasma. Form B is to be preferred as internal standard in turbidimetric and nephelometric indirect lipase assays.     

Evidence for conformers of rabbit muscle adenylate kinase

Changes of the apparent Mr values and the circular dichroism patterns suggest the existence of three relatively stable conformers of rabbit muscle adenylate kinase (RMAK). The effects of dithiothreitol (DTT) which stimulates activity, pH, the substrates, and ATP on the Mr value and the Stokes radius of RMAK were determined from gel filtration data, and apparent Mr values near 22,000, 26,000, and 29,000 resulted. Substrates generated multiple Mr values, suggesting the presence of multiple conformers of RMAK. The higher apparent Mr values were obtained in the presence of DTT and at the higher substrate concentrations, indicating more open conformations. The effect of the substrates on the conformation of RMAK is discussed in relation to the kinetic mechanism of this random bireactant system. Circular dichroism studies were undertaken in order to observe any changes in the secondary structures of RMAK in relation to changes of the Mr values. The secondary structure composition of RMAK, determined under our conditions, does not agree with results determined from crystallographic studies. The gel filtration and the CD studies suggest that above pH 7 a more open conformation of RMAK obtains in the presence of DTT. The results of these studies are discussed with reference to the location of the active sites.     

Evidence for receptor-mediated uptake of adenosine deaminase in rabbit kidney

We investigated the subcellular location of adenosine deaminase-complexing protein in the proximal renal tubules of rabbit kidney and its interaction with intravenously infused monomeric calf adenosine deaminase. Cortical tissue from non-infused animals, stained in suspension by the peroxidase-antiperoxidase method for complexing protein and embedded in resin, was examined by transmission electron microscopy. Positive staining indicated the presence of complexing protein on the surface of microvilli in the proximal tubules. Sections (1 micron) of resin-embedded cortex from infused rabbits, stained first for complexing protein and then for adenosine deaminase, were examined by light microscopy. After staining for complexing protein by indirect immunofluorescence, the sections were photographed and then immersed in buffer containing 6 M guanidine hydrochloride plus 2-mercaptoethanol for 3 hr at 60 degrees C to remove bound antibodies. The sections were then stained by the peroxidase-antiperoxidase method for infused enzyme. Vesicle-like apical structures, the basal membrane area and, as previously reported, the brush border of proximal tubule cells were positive for complexing protein. Vesicle-like structures and brush borders positive for complexing protein were also stained for adenosine deaminase. The basal membrane area did not stain. These results support the hypothesis that complexing protein can act as a receptor for adenosine deaminase.     

Characterization by polyacrylamide gel electrophoresis of hemoglobins in rabbit embryo, fetus, and adult

The hemoglobin species of rabbit embryo, fetus, and adult were characterized by quantitative polyacrylamide gel electrophoresis (PAGE). Special statistical methods, including joint confidence envelopes for the slope (K_R) and intercept (Y₀) of the Ferguson plot and analysis of covariance were utilized to identify the hemoglobin species. Five embryonic rabbit hemoglobins could be distinguished. Their relative proportions varied with developmental stage. No specific fetal hemoglobin was detected. The two previously known adult hemoglobins were characterized, prepared by isoclectric focusing on polyacrylamide gel (IFPA) and shown to differ by two amino acid substitutions in the β-chain.A general strategy for testing molecular identity by PAGE is outlined.     

Carnivory maintains cranial dimorphism between males and females: Evidence for niche divergence in extant Musteloidea

The evolution and maintenance of sexual dimorphism has long been attributed to sexual selection. Niche divergence, however, serves as an alternative but rarely tested selective pressure also hypothesized to drive phenotypic disparity between males and females. We reconstructed ancestral social systems and diet and used Ornstein–Uhlenbeck (OU) modeling approaches to test whether niche divergence is stronger than sexual selection in driving the evolution of sexual dimorphism in cranial size and bite force across extant Musteloidea. We found that multipeak OU models favored different dietary regimes over social behavior and that the greatest degree of cranial size and bite force dimorphism were found in terrestrial carnivores. Because competition for terrestrial vertebrate prey is greater than other dietary groups, increased cranial size and bite force dimorphism reduces dietary competition between the sexes. In contrast, neither dietary regime nor social system influenced the evolution of sexual dimorphism in cranial shape. Furthermore, we found that the evolution of sexual dimorphism in bite force is influenced by the evolution of sexual dimorphism in cranial size rather than cranial shape. Overall, our results highlight niche divergence as an important mechanism that maintains the evolution of sexual dimorphism in musteloids.     

Evidence for imidazoline binding sites in basolateral membranes from rabbit kidney

[3H]-RX 781094 and [3H]-rauwolscine, two potent alpha 2-adrenergic antagonists, were used to characterize alpha 2 receptor in basolateral membranes from rabbit kidney. However, the following findings suggest that the imidazoline [3H]-RX 781094 binds to an heterogeneous population of binding sites: 1) dissociation plot was biphasic with a fast and slow component, 2) in saturation experiments, [3H]-RX 781094 labels 3.5 more binding sites than [3H]-rauwolscine (p less than 0.02), 3) competition studies showed that molecules with imidazoline structure completely inhibited the [3H] RX 781094 binding; in contrast, only 25% of binding was affected by non-imidazoline alpha 2 adrenergic compounds. These results suggest that in basolateral membranes from rabbit kidney, [3H] RX781094 labels alpha 2 adrenergic and non-adrenergic receptors which might be imidazoline-preferring binding sites.     

Evidence for a single steroid-binding protein in the rabbit progesterone receptor

The rabbit uterine progesterone receptor copurifies as two molecular weight (Mr) forms of about 105,000 and 78,000. To investigate whether these are different proteins, we have used protease digestion, reversible denaturation, and photoaffinity labeling in studies on the steroid-binding domain of the receptor. Digestion of the Mr 105,000 and 78,000 forms, photoaffinity labeled with [3H]R5020, with Staphylococcus aureus V8 protease revealed identical peptide fragments of Mr 43,000, 39,000, and 27,000-30,000. When receptor in cytosol was denatured, separated by electrophoresis, and then reconstituted, [3H]progesterone bound specifically to a single form at about Mr 105,000. After partial purification, the reversible denaturation procedure revealed both the larger and the smaller progesterone-binding species similar to the photoaffinity-labeled species in this preparation. Receptor in uterine cytosol prepared under mild conditions appeared as a predominant large molecular weight form on photoaffinity labeling with [17 alpha-methyl-3H]R5020, [6,7-3H]R5020, or [3H]RU27987. Further purification of this cytosol showed the generation of a smaller labeled species. These results from three different approaches reinforce the view that the rabbit progesterone receptor contains a single steroid-binding protein.     

Evidence for oxytocin receptors in the urinary bladder of the rabbit

Experiments were performed on isolated detrusor smooth muscle from New Zealand White rabbits. Oxytocin was shown to exhibit high intrinsic contractile activity on isolated strips of detrusor muscle, where the maximum contractile amplitude was 12% greater than control responses to 1 microM carbachol. Repeated applications of 1 microM oxytocin were associated with tachyphylaxis representing a 49% decrease in the amplitude which became reproducible after several applications without further decay of contractile strength. Dose-response experiments indicated that threshold contractions to oxytocin occur at 3 nM and were maximum at 10 microM with mean effective concentration of 125 nM. The contractile responses to 1 microM oxytocin were not antagonized by phentolamine, atropine, methysergide, saralasin, or naloxone, but were partially inhibited by 1 microM of indomethacin. Ligand binding studies on partially purified membrane preparations from detrusor smooth muscle were performed over a range of 78 pM to 10 nM with 125I-labelled oxytocin. Scatchard analysis of specific bound receptors indicated a KD of 2.5 nM and Bmax of 187 fmol/mg protein and a second compartment that was unsaturable at the concentrations of ligand employed. Nonspecific binding ranged from 36 to 77% of the total binding.     

Evidence for basal secretion in the subcommissural organ of the adult rabbit

Summary Morphological evidence is presented supporting the possibility of basal secretion into hypendymal capillaries of the adult rabbit subcommissural organ (SCO). The synthetic apparatus of the SCO cell is described as well as the heterogeneous granules and vesicles which are concentrated in the basal processes bordering a widened perivascular space. The origin of the electron dense granules, of which two fairly distinct subgroups are found, is discussed.A binding of secretory sacs to the lateral plasma membrane is seen. The possibility of a lateral secretion is supported by the presence of a system of extracellular channels between SCO cells which are filled with a flocculent material resembling that of the secretory sacs.Nerve perikarya which are separated from the SCO by only a few glial fibers are demonstrated. Synapses are described in nerve fascicles bordering on the hypendymal capillaries. The possibility of an innervation of the hypendymal region is discussed as well as possible nervous connections with the pineal gland.This work was supported by grants from Statens almindelige Videnskabsfond, Copenhagen.