Pro-opiomelanocortin peptides in the human fetal pituitary

Levels of immunoreactive pro-opiomelanocortin (POMC) peptides (N- and C-terminal ACTH, N- and C-terminal LPH and α-MSH) have been measured in pituitary extracts from human fetuses of 12–22 weeks gestation. The levels of ACTH were 30–200 times higher than α-MSH in all fetuses studied. Sephadex G-75 and G-25 chromatography of 8 extracts showed peaks of 34 kilodaltons (K) POMC, 22K ACTH, β-LPH, γ-LPH, β-endorphin, approximately 8K ACTH, 1–39 ACTH, α-MSH and CLIP. The 8K and 22K forms of ACTH are both partly glycosylated.In vitro culture of pituitaries from 2 fetuses (22 and 26 weeks gestation) gave a detectable basal output of ACTH but not of α-MSH. Stimulation of these pituitary cells with human fetal and rat hypothalamic extracts and with synthetic ovine CRF-41 produced a significant increase in ACTH release, and either small or undetectable amounts of α-MSH.These results demonstrate the presence of POMC-related peptides in early gestation human fetal pituitaries and suggest that ACTH, and not α-MSH, is the major corticotrophic hormone at this stage of gestation.     

CYTOLOGICAL AND CHEMICAL VARIATION IN PITYROGRAMMA TRIANGULARIS

The cytology and chemistry of three populations of the species complex Pityrogramma triangularis from Santa Barbara County, California, were studied. The basic chromosome number of these ferns is x = 30, and there are diploids, triploids, and tetraploids. Although gross morphology in the plants is similar, four chemical types are observed when extracts of the external frond pigments are analyzed. Ten of the twelve possible combinations of ploidy level and pigment types have been found. Correlations of spore condition, cytology, and chemistry which indicate either an autotetraploid or allotetraploid derivation of the complex are discussed.     

Environmental effects on bacterial copper extraction from low-grade copper sulfide ores

In bacterial extraction of copper from low-grade copper sulfide ores, at least three contributions are made by Thiobacillus ferrooxidans. They are: (1) enzymatic oxidation and consequent solubilization of insoluble sulfides; (2) regeneration of ferric lixiviant for chemical oxidation and solubilization of insoluble sulfides; and (3) partial fixation of externally introduced iron in the ore. Although it is not possible at the present time to measure each of these contributions separately, it is possible to measure the combined contributions. Such measurements reveal a strong dependence of extraction efficiency on various physical, chemical, and biological factors. The following physical factors may affect the rate of bacterial copper extraction: particle-size of ore, oxygen and carbondioxide supply, oxidation-reduction potential, pH, temperature, adsorption and ion exchange capacity of ore, and surface tension effects. The following chemical factors may influence the rate of copper extraction: the mineralogy of the ore, the nature of the gangue, the distribution of the sulfide minerals in the host rock, the external supply of ferrous or ferric iron, and the availability of inorganic and organic nutrients. Finally, the following biological agents in addition to T. ferrooxidans may influence the rate of copper extraction: fungi, protozoa, Thiobacillus thiooxidans, and heterotrophic bacteria. Proper control of these various factors is essential for efficient bacterial extraction of copper from low-grade ore. It is recognized that the foregoing environmental factors also influence chemical copper extraction.     

Hermaphroditism in icerya zeteki cockerell,and the mechanism of gonial reduction in iceryine coccids (coccoidea: Margarodidae morrison)

In the Panamanian iceryine coccid Icerya zeteki Cockerell (Family Margarodidae Morrison) all females become hermaphroditic early in the first instar; occasional males arise from unfertilized eggs, but self-fertilization is assured by the protandry of the hermaphrodite. In the development of the ovotestis, initiation of the male phase is brought about by haploidization of those germ cells destined for spermatogenesis. In both Icerya zeteki and Icerya purchasi this gonial reduction results from the degeneration and elimination of one genome during prophase. Except for minor variations in the coiling cycle of spermatocytes, the chromosomes (n=2) of I. zeteki correspond closely to those of all other haplo-diploid iceryines known. The present status of the species Icerya zeteki Cockerell is reviewed, and on both taxonomicand cytological grounds is judged to be uncertain.Supported in part by National Science Foundation Grant GB — 1922.     

The elimination and differentiation of chromosomes in the germ line of sciara

The germ line chromosomes of S. coprophila have been followed from the time of origin of the germ cells up to the time of meiosis in the male and up to first larval molt in the female. The mechanism which prevents the accumulation of L (limited) chromosomes in the germ line is a unique process of chromosome elimination: it occurs in male and female embryos after the germ cells have migrated from the pole plasm to the definitive gonad site, and it involves the movement of whole L chromosomes through the nuclear membrane into the cytoplasm. The extra paternal X chromosome is eliminated from the germ cells at the same time and in the same manner. Following this elimination there is a cytological differentiation of the chromosomes remaining inside the nucleus. First, the 4 paternal homologues of the regular complement undergo a loosening of coils and become light-staining whereas the maternal homologues remain condensed like the L's. Next, the L chromosomes undergo a process of extreme attenuation and dispersion following which they return to the condensed state. H³-thymidine autoradiography on gonial and premeiotic cells in the testis reveals that the L chromosomes undergo DNA replication at the end of the S period, also that there are asynchronies in DNA synthesis among the regular chromosomes. The phenomena of differential chromosome staining and asynchronous DNA replication are considered in the light of current theory regarding heterochromatization and gene inactivation, also in relation to the phenomenon of chromosome imprinting encountered in this genus.The studies reported here were supported by the National Science Foundation grants GB-42 and GB-2857, and in part by Contract No. AT-(40-1)-2690 under the Division of Biology and Medicine, U.S. Atomic Energy Commission.Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy, in the Faculty of Pure Science, Department of Botany, Columbia University. This work was carried out in the laboratory of Professor J. Herbert Taylor and has been supported in part by U.S. Public Health Training Grant No. 2 T 1-GM-216-05. Grateful acknowledgement is made to Professor Spencer W. Brown, Department of Genetics, University of California, Berkeley, in whose laboratory the final studies were completed.     

A rapid method for the detection of potentially viable Mycobacterium leprae in human biopsies: a novel application of PCR

Abstract A simple procedure based on the polymerase chain reaction has been developed to detect Mycobacterium leprae , rapidly and unambiguously, in biological samples. Its application to small numbers of M. leprae cells (∼ 10²) isolated from armadillo liver, mouse footpads or human biopsies is discussed.     

Variability of entrainment of cohesive sediments in freshwater

Estimates of sediment entrainment are required for models of particle transport in lakes and estuaries but are difficult to make because of the multiplicity of factors affecting cohesiveness of surficial sediments. We present results of sediment resuspension studies performed in an annular flume calibrated with laser-Doppler velocimetry. In our experiments, using sediments collected from two sites in the R. Raisin which flows into L. Erie and from one site in the western basin of L. Erie near the mouth of the R. Raisin, we applied shear stresses at the sediment-water interface in steps from 2 to 12 dyne/cm². Percent water content at the surface of the sediments was either 77 or 74%, and trials were run with and without oxygenating the water overlying the sediments. Entrainment rates as a function of shear stress at the sediment-water interface were best described by a power-law relationship. All but 14% of the variability in the power law expression was due to shear stress and percent water content; the variability not accounted for was due to differences in particle size distributions, chemical properties, and biological activity in the sediments.     

Increased Neostriatal Tyrosine Hydroxylation During Stress: Role of Extracellular Dopamine and Excitatory Amino Acids

Abstract: We examined the regulation of neostriatal tyrosine hydroxylation during acute stress, testing the hypothesis that excitatory amino acids (EAAs) contribute to the stress-evoked increase in dopamine (DA) synthesis. Dialysis probes implanted into neostriatum permitted delivery of drugs and sampling of extracellular fluid. Rats were exposed to 30 min of intermittent tail shock during infusion of an inhibitor of aromatic amino acid decarboxylase (AAAD), NSD-1015 (100 µM), and DOPA was measured in the dialysate. Tail shock was applied beginning either 15 min after the onset of NSD-1015 treatment (the initial rate of DOPA accumulation) or 75 min after the onset of treatment (when DOPA had approached steady state). Tail shock increased the steady-state levels of extracellular DOPA in neostriatum (+40%). However, there was no change in the initial rate of DOPA accumulation unless animals also received the D₂ receptor antagonist eticlopride (50 nM), in which case an increase was observed (+228%). The impact of tail shock on the steady-state level of DOPA was attenuated by the D₂ agonist quinpirole (100 µM), or by 2-amino-5-phosphonovalerate (APV) (100 µM) or 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) (100 µM), EAA antagonists acting at NMDA or d ,l -α-amino-3-hydroxy-5-methyl-4-isoxazole-4-propionate (AMPA) receptors, respectively. These data suggest that acute stress normally has little effect on tyrosine hydroxylation in neostriatum due to the inhibitory influence of DA in the extracellular fluid. However, when that influence is absent (e.g., during extended inhibition of DOPA decarboxylation or blockade of DA receptors), stress increases tyrosine hydroxylation via EAAs acting on NMDA and AMPA receptors. Thus, EAAs released from corticostriatal projections may stimulate DA synthesis and thereby restore dopaminergic activity under conditions in which the availability of DA for release has been compromised.     

Analysis of HLA and Disease Susceptibility: Chromosome 6 Genes and Sex Influence Long-QT Phenotype

The long-QT (LQT) syndrome is a genetically complex disorder that is characterized by syncope and fatal ventricular arrhythmias. LQT syndrome, as defined by a prolonged electrocardiographic QT interval, has a higher incidence in females than in males and does not exhibit Mendelian transmission patterns in all families. Among those families that are nearly consistent with Mendelian transmission, linkage between a locus for LQT syndrome and the H-ras-1 locus on the short arm of chromosome 11 has been reported in some families but not in others. Earlier analyses suggesting that LQT syndrome might be caused by a gene in the HLA region of chromosome 6 were not confirmed by standard linkage analyses. Here, we present an analysis of HLA haplotype sharing among affected pedigree members, showing an excess of haplotype sharing in a previously published Japanese pedigree and possibly also in 15 families of European descent. The haplotypes shared by affected individuals derive from both affected and unaffected parents. In an analysis of independent (unrelated) HLA haplotypes, we also found a nonrandom distribution of HLA-DR genes in LQT syndrome patients compared with controls, suggesting an association between the LQT phenotype and specific HLA-DR genes. Our data indicate that DR2 has a protective effect and, particularly in males, that DR7 may increase susceptibility to the LQT syndrome. Thus, LQT syndrome may be influenced by genes on chromosomes 11 and 6, possibly with a sex-specific effect. These results provide a model for an effect of HLA-region genes inherited from either parent on the expression of an illness that may be determined principally by alleles at loci not linked to HLA.     

Stress-Induced Sensitization of Dopamine and Norepinephrine Efflux in Medial Prefrontal Cortex of the Rat

Abstract: We examined whether prior exposure to chronic cold (17–28 days, 5°C) alters basal or stress-evoked (30-min tail shock) catecholamine release in medial prefrontal cortex, nucleus accumbens, and striatum, using in vivo microdialysis. Basal norepinephrine (NE) concentrations in medial prefrontal cortex did not differ between chronically cold-exposed rats and naive control rats (2.7 ± 0.3 vs. 2.5 ± 0.2 pg/20 µl, respectively). Basal dopamine (DA) efflux in any of the brain regions was not significantly different between chronically cold-exposed rats and naive rats. However, a trend for lower basal DA efflux in the cold-exposed relative to naive rats was observed in medial prefrontal cortex (1.5 ± 0.2 vs. 2.2 ± 0.3 pg/20 µl, respectively), nucleus accumbens (3.7 ± 0.8 vs. 5.4 ± 0.9 pg/20 µl, respectively), and striatum (4.4 ± 0.5 vs. 7.2 ± 1.5 pg/20 µl, respectively). In medial prefrontal cortex of rats previously exposed to cold, tail shock elicited a greater increase from baseline in both DA and NE efflux relative to that measured in naive rats (DA, 2.3 ± 0.3 vs. 1.2 ± 0.1 pg, respectively; NE, 3.8 ± 0.4 vs. 1.4 ± 0.2 pg, respectively). However, in nucleus accumbens or striatum of rats previously exposed to cold, the stress-induced increase in DA efflux was not significantly different from that of naive rats (nucleus accumbens, 1.8 ± 0.7 vs. 1.5 ± 0.3 pg, respectively; striatum, 1.9 ± 0.4 vs. 2.6 ± 0.7 pg, respectively). Thus, both cortical NE projections and cortically projecting DA neurons sensitize after chronic exposure to cold. In contrast, subcortical DA projections do not sensitize under these conditions.