Reconstruction of the lacrimal excretory system.

Primary surgical repair of the lacrimal drainage apparatus may not be feasible in patients with maxillofacial injuries involving extensive structural damage. If secondary restoration of the tear duct is not possible, reconstruction of an aberrant passage then will be necessary for tear drainage. Although the Pyrex conjunctivorhinostomy has been considered to be the most effective modality of treatment in managing patients with tear-duct dysfunction, this procedure can be plagued with problems of tube dislodgment, infection, and cicatricial tract obliteration. The patients are, furthermore, required to wear the device for the remainder of their lives. Autologous material is therefore best suited for reconstructing a conduit. A medially based mucosal flap fashioned in the lower palpebral conjunctiva, 5 mm in anteroposterior dimension and 15 mm in horizontal length, can be used to form a conduit. This is then sutured to a flap mobilized from the nasal cavity, the lacrimal sac, or the maxillary antrum. In the past 15 years, a total of 24 fistulous tracts utilizing this technique were reconstructed in 20 patients with tear-duct obstruction. The experience accumulated from managing this group of patients forms the basis of this report.     

Diurnal variation of dopamine content in the rat pineal gland

Levels of norepinephrine and dopamine in the rat pineal gland were determined by a radioenzymatic assay with modifications to separate the reaction products. Catecholamines were converted to 3-O-methylated derivatives in the presence of catechol-O-methyltransferase (EC 2.1.1.1) and S-adenosyl-L-[methyl-³H]-methionine. Following solvent extraction of the labelled normetanephrine and 3-methoxytyramine, the amines were separated by high-performance liquid chromatography. Contents of both catecholamines in the pineal gland varied with a 24-hr rhythm. The content of norepinephrine was maximal at about 6 A.M. (lights on from 8 A.M. to 8 P.M.) and declined gradually thereafter. In contrast to the level of norepinephrine, the dopamine level was highest at about 0 A.M. and fell rapidly to reach a trough after the lights were turned on. These observations suggest that the diurnal variation of norepinephrine is generated by changes in the contents of dopamine in sympathetic nerve terminals innervating the pineal.     

Nucleotide sequence of mouse Tcp-1a cDNA

We have isolated complete cDNA clones encoding the mouse t-complex polypeptides 1A and 1B (TCP-1A and TCP-1B) from t-haplotype and wild-type (wt) mice, respectively. The complete nucleotide (nt) sequence of the Tcp-1a cDNA was determined. The Tcp-1a cDNA has an open reading frame (ORF) encoding a 60-kDa protein of 556 amino acids (aa). A comparison of nt sequences between the Tcp-1a and Tcp-1b cDNAs revealed that the 1786-bp regions upstream from their polyadenylation signals differed by 17 substitutions and that Tcp-1a had different polyadenylation sites from Tcp-1b. In these ORFs, 15 bp were substituted between the two alleles, occurring in 14 codons and resulting in eleven single-aa substitutions. Among these 15 substitutions, twelve were nonsynonymous (aa change) and three were synonymous (no aa change). The aa substitution in TCP-1 has occurred at least 20 times faster between t-haplotype and wt than between mouse and human or mouse and Drosophila.     

Enzyme catalyzed acylation and deacylation of the sugar moieties of nucleosides

We have found that a lipase from Pseudomonas fluorescens (PFL) accelerated regioselective acylation of 2'-deoxynucleosides with the use of acid anhydrides as acyl donor in dry polar solvents. Different regioselective deacylation of 3',5'-di-O-acyl-2'-deoxynucleosides was found to take place when a lipase (PFL) or a protease from Bacillus subtilis (Subtilisin) was used.     

Flow threshold for enhanced phorbol ester binding in the ischemic gerbil brain

The correlation between regional phorbol ester binding and cerebral blood flow (CBF) was evaluated in the gerbil brain after 2-hour unilateral common carotid artery occlusion [³H]phorbol 12, 13-dibutyrate (PDBu) was used as a specific ligand for estimating the translocation of protein kinase C (PKC), and CBF was determined by the [¹⁴C]iodoantipyrine method. A quantitative autoradiographic method permitted concurrent measurement of these two parameters in the same brain. In the ischemia group of the animals, statistically significant, inverse correlations were noted between the CBF and PDBu binding in the hippocampus (CA₁ and CA₃ regions and dentate gyrus), the caudate-putamen and lateral nuclei of the thalamus. In these regions, the PDBu binding increased progressively as CBF fell below 35–40 ml/100 g/min. On the other hand, the PDBu binding in the cerebral cortices did not show any significant changes even when CBF was decreased to below 35 ml/100 g/min. The above data suggest that (1) the translocation of PKC to the cell membrane may be regionally specific in response to ischmia and may remain in the regions particularly vulnerable to ischemia such as the hippocampus, caudate-putamen and lateral nuclei of the thalamus in the early ischemic phase; (2) the threshold of CBF below which PKC begins to translocate to the cell membrane in the above regions, may be 35–40 ml/100 g/min in 2-hour ischemia.     

MORPHOLOGY AND PAEDOGAMOUS SEXUAL REPRODUCTION IN CHLOROGONIUM CAPILLATUM SP. NOV. (VOLVOCALES, CHLOROPHYTA)1

Morphology and sexual reproduction in Chlorogonium capillatum Nozaki, Watanabe & Aizawa sp. nov. (Volvocales, Chlorophyta) originating from Miyatoko Mire, Japan, were studied under controlled laboratory conditions. Vegetative cells of this new species were fusiform with blunt anterior and posterior ends, and they had a massive parietal chloroplast and numerous contractile vacuoles distributed throughout the protoplast. Several to many pyrenoids were randomly distributed in the chloroplast, but they disappeared under the light microscope when grown photoheterotrophically. During asexual reproduction, the first division took place transversely without a preceding rotation of the parental protoplast. In sexual reproduction, the parental protoplast divided successively to form 32 or 64 small, biflagellate isogametes. After gametogenesis, the gametes did not escape from the parental cell (gametangial) wall, within which pairs of the adjoining gametes fused to form quadriflagellate zygotes. Such zygotes were then released from the parental cell wall and developed into hypnozygotes, which at maturity developed numerous thin spines or hairs on the zygote wall. On zygote germination, four biflagellate germ cells were released from the zygote wall separately. This type of gametic union, "paedogamy," has not previously been described in the green algae except for Chlorococcum echinozygotum Starr . Chlorogonium capillatum can be clearly distinguished from other described species of Chlorogonium by its numerous contractile vacuoles and blunt anterior and posterior ends in vegetative cells as well as by its unique sexual reproduction, in which paedogamous conjugation occurs, and numerous thin spines or hairs that develop on the hypnozygote walls .     

Two bases are eliminated from DNA by treatment with bleomycin or with hemin-intercalators

A hemin-intercalator, H4G-His, which possesses 2-amino-6-methyldipyrido[1,2-a:3',2'-d]imidazole (Glu-P-1) as an intercalator moiety and histidine as an intramolecular ligand of the ferrous ion of the hemin ring, cleaves DNA very efficiently, and acts at guanine-pyrimidine sequences preferentially. Bleomycin (BLM) also cleaves DNA with the same base-sequence selectivity shown by H4G-His. The 5'-terminal of the DNA fragments cleaved by H4G-His or by BLM bears a phosphoryl group, while the 3'-terminal of the cleaved DNA fragments does not possess a 3'-phosphoryl group. There are three (or more) kinds of structures of the 3'-terminals. One of the structures of the 3'-terminals of the cleaved DNA fragments is a free 3'-hydroxy group. We propose that there exist plural mechanisms for DNA cleavage by H4G-His or by BLM, one of which involves elimination of two bases from DNA.     

ASEXUAL AND SEXUAL REPRODUCTION IN GONIUM QUADRATUM (CHLOROPHYTA) WITH A DISCUSSION OF PHYLOGENETIC RELATIONSHIP WITHIN THE GONIACEAE1

Morphological details of asexual and sexual reproduction in Gonium Quadratum Pringsheim ex Nozaki (Goniaceae, Chlorophyta) were observed by light microscopy, based on clonal cultured materials originating from Nepal. In asexual reproduction, the alga exhibited two different patterns of cell cleavage during formation of 8-and 16-celled daughter colonies. Sexual reproduction was heterothallic and isogamous. The gametes bore a tubular mating structure (bilateral mating papilla) at the base of the flagella, and the papillae of the two gametes. The germinating zygote gave rise to four biflagellate gone cells joined in a colony (germ colony). Possible phylogenetic relationships within the Goniaceae at the species level are outlined, mainly on the basis of reproduction characteristics.     

The Entamoeba histolytica Dnmt2 Homolog (Ehmeth) Confers Resistance to Nitrosative Stress

Nitric oxide (NO) has antimicrobial properties against many pathogens due to its reactivity as an S-nitrosylating agent. It inhibits many of the key enzymes that are involved in the metabolism and virulence of the parasite Entamoeba histolytica through S-nitrosylation of essential cysteine residues. Very little information is available on the mechanism of resistance to NO by pathogens in general and by this parasite in particular. Here, we report that exposure of the parasites to S-nitrosoglutathione (GSNO), an NO donor molecule, strongly reduces their viability and protein synthesis. However, the deleterious effects of NO were significantly reduced in trophozoites overexpressing Ehmeth, the cytosine-5 methyltransferase of the Dnmt2 family. Since these trophozoites also exhibited high levels of tRNA^Asp methylation, the high levels suggested that Ehmeth-mediated tRNA^Asp methylation is part of the resistance mechanism to NO. We previously reported that enolase, another glycolytic enzyme, binds to Ehmeth and inhibits its activity. We observed that the amount of Ehmeth-enolase complex was significantly reduced in GSNO-treated E. histolytica, which explains the aforementioned increase of tRNA methylation. Specifically, we demonstrated via site-directed mutagenesis that cysteine residues 228 and 229 of Ehmeth are susceptible to S-nitrosylation and are crucial for Ehmeth binding to enolase and for Ehmeth-mediated resistance to NO. These results indicate that Ehmeth has a central role in the response of the parasite to NO, and they contribute to the growing evidence that NO is a regulator of epigenetic mechanisms.