Stereoselective reduction with NADH model BNAH through chiral induction in cyclodextrins.

Stereoselective reductive debromination-cyclopropanation of 2-bromo-1-phenylethylidene-malononitrile and 2-bromo-1-beta-naphthylethylidenemalononitrile by coenzyme NADH model BNAH through chiral induction in cyclodextrins is reported. The matching between substrates and cyclodextrins, the substituent effect, and the effect of cyclodextrin concentration on the optical yields have been investigated.

A study on the enthalpy-entropy compensation in protein unfolding.

A large number of thermodynamic data including the free energy, enthalpy, entropy, and heat capacity changes were collected for the denaturation of various proteins. Regression indicated that remarkable enthalpy-entropy compensation occurred in protein unfolding, which meant that the change in enthalpy was almost compensated by a corresponding change in entropy resulting in a smaller net free energy change. This behavior was proposed to result from the water molecule reorganization, which contributed significantly to the enthalpy and entropy changes but little to the free energy change in protein unfolding. It turned out that the enthalpy-entropy compensation could provide novel insights into the problem of enthalpy and entropy convergence in protein unfolding.

Development of gamma-aminobutyric acid-immunoreactive neurons in normal and intracranially transplanted retinas in rats.

Retinas from embryonic day 14 Sprague-Dawley rats were transplanted intracranially to the midbrain or cortex of newborn (P0) rats with right eyes enucleated at the time of transplantation and the gamma-aminobutyric acid (GABA) immunoreactivity in developing retinal transplants, host as well as normal retinas, was studied. The results showed that GABA-immunoreactive neurons were identified in retinas of normal and host rats from the day of birth (P0) onward and that their somata were distributed primarily in the inner half of the internal nuclear layer and in the ganglion cell layer. The adult pattern of GABA immunoreactivity was first observed at P16 when several immunoreactive sublaminae were clearly identifiable in the inner plexiform layer. In contrast, gamma-aminobutyric acid-immunoreactive somata could not be identified in retinal transplants until P4, with a significant reduction in the density and number of GABAergic neurons detected by P12. Moreover, only two immunoreactive sublaminae were observed in the inner plexiform layer in all transplants at P12, as well as in more mature stages. These results suggest that significant changes occurred in the GABA system of the transplanted retina, despite the fact that the overall pattern of organization of the GABAergic neurons and their processes in the retinal transplants was comparable to that of the normal retina.

Development of parvalbumin immunoreactive neurons in normal and intracranially transplanted retinas in the rat.

Retinas from embryonic day 14 Sprague-Dawley rats were transplanted to the midbrain or cerebral cortex of newborn (P0) rats of which the right eye was enucleated at the time of transplantation. Parvalbumin immunoreactive (PV-I) neurons were studied in the developing retinal transplants, and in the remaining retina of the host, as well as in normal retinas. PV-I neurons were identifiable in retinas of normal and host rats from postnatal day 5 (P5) onward, with the PV-I somata primarily in the inner half of the inner nuclear layer and in the ganglion cell layer. An adult-like distribution of PV-I neurons was attained at P35, as judged by cell packing density, intensity of immunostaining, laminar distribution and soma size of subpopulations of PV-I cells. A similar time course of development and distribution of PV-I somata was observed in the retinal transplants, except for some minor differences such as a slight delay in PV-I cells achieving their final distribution. These findings provide evidence that PV-I neurons can survive, differentiate and mature according to predetermined programmes intrinsic to the retinal tissue following transplantation to a new and foreign environment.

Tyrosine-hydroxylase-immunoreactive neurons in retinal transplants in the rat.

Embryonic rat retinae were transplanted to the brains of newborn rats, and the distribution of catecholaminergic neurons in the retinal tissue was studied 1-2 months after transplantation, using the tyrosine hydroxylase (TH) immunohistochemical method. The results showed that distinct TH-positive cells were identified in all retinal transplants examined. The somata of the majority of these TH-immunoreactive cells were located along the inner margin of the inner nuclear layer in the retinal transplants; the processes of these cells were distributed mainly in the outer portion of the inner plexiform layer. This pattern is comparable to that observed in retinae of normal and host rats, suggesting that the organization of the catecholaminergic neurons in the transplant is largely similar to that in the normal retina. However, a reduction of the immunoreactivity in the plexiform layers and subpopulations of TH-positive cells with somatic diameter smaller than 8 microns or larger than 18 microns was observed in most of the retinal transplants studied. This implies that the organization of the catecholaminergic system in the transplant may not be as intact as in the normal retina.

Development of choline acetyltransferase-immunoreactive neurons in normal and intracranially transplanted retinas in rats.

Retinas from embryonic day 14 (E14) Sprague-Dawley rats were transplanted to the tectum of newborn (P0) recipient rats, and the distribution pattern of choline acetyltransferase immunoreactivity (ChAT-I) in developing transplants was studied and compared with those observed in the retinas of normal developing rats. In normal retinas, ChAT-I cells were first identified in restricted regions in the ganglion cell layer (GCL) at P4, but were found to cover the entire GCL by P6. A second population of ChAT-I cells was detected in the inner nuclear layer (INL) at P8, and they were observed in most parts of the INL on P10 when two immunoreactive sublaminae began to appear in the inner plexiform layer (IPL). The adult pattern of having two distinct populations of ChAT-I cells, organized in mirror symmetrical fashion in the inner retinal layers was basically established by P12. The time course of development and overall distribution pattern of ChAT-I cells in developing retinal transplants on the whole were very similar to those observed in normal retinas. The first identification of these cells and the establishment of their final distribution pattern were made at stages corresponding to P4 and P12 of normal developing retinas respectively. However, ChAT-I somata were located in the INL at a much earlier stage compared with their counterparts in the normal retina, and a transient population of immunoreactive cells with their processes extending to retinal layers other than the IPL was observed in some transplants from P6 to P10. These features were not observed in normal developing retinas. These results suggest that the development of cholinergic neurons, especially the expression of their characteristic antigen and their final distribution pattern is largely determined by programmes which are intrinsic to the original retinal tissue, despite some minor deviation or variation in the developmental process which may occur under certain abnormal conditions.