Inhibition of the glucose-6-phosphatase system by N-bromoacetylethanolamine phosphate, a potential affinity label for auxiliary proteins

N-Bromoacetylethanolamine phosphate (BAEP) has been used previously as an affinity label to study the hexose phosphate binding sites of fructose-6-P, 2-kinase:fructose-2, 6-bisphosphatase (Sakakibara et al. (1984) J. Biol. Chem. 259, 14023-14028). We have employed this compound to probe components of the glucose-6-phosphatase system using a combination of time-dependent and immediate inhibition kinetic techniques. Inhibition of D-glucose-6-phosphate (G6P) phosphohydrolase activity of native microsomes was irreversible and time- and inhibitor-concentration-dependent. Only a partial time-dependent, irreversible inhibition of the PPi phosphohydrolase activity of native microsomes was observed. BAEP inhibited PPi:glucose phosphotransferase activity of native microsomes in a concentration-dependent, irreversible manner which was more extensive than that seen with PPi phosphohydrolase, but less extensive than was observed with G6P phosphohydrolase. Disruption of microsomal integrity by detergent-treatment either prior to incubation with BAEP or subsequent to preliminary incubation with BAEP but prior to assay for activity abolished the time-dependent inhibition. These irreversible, time- and concentration-dependent inhibitory actions of BAEP thus are manifest at a site or sites where the intact membrane-bound enzyme first makes contact with substrates G6P and PPi. An additional site of inhibition by BAEP, through relatively weak, reversible competitive inhibition at the active catalytic site, is indicated by classical steady-state kinetic analysis. The irreversible, time- and concentration-dependent inhibitions by BAEP seen with G6P and PPi as substrates strongly suggest the potential utility of radio-labeled BAEP as an affinity label for the identification and ultimate isolation and study of uncharacterized auxiliary components of the glucose-6-phosphatase system.

Observations on the transmission of scrapie in experiments using embryo transfer

This investigation studied the maternal transmission of scrapie in sheep by using embryo transfer to examine the viability of highly susceptible offspring derived from scrapie-affected and uninfected donors. The study also examined the effect of washing the embryos. Scrapie occurred in both washed and unwashed embryo-derived Sip sAsA progeny from both groups of donor ewes. As a result, the earlier observation that scrapie might pass via the unwashed embryo to develop as disease in adult sheep has to be reassessed. Several other implications of the work are considered, including the possibility that natural scrapie is not purely a genetic disease.

Natural scrapie in a closed flock of Cheviot sheep occurs only in specific PrP genotypes

Natural scrapie in a closed flock of South Country Cheviot sheep has resulted in 45 deaths between 1986 and 1995. Of these cases, 35 sheep have been analysed for disease-linked PrP gene polymorphisms and all encode valine at codon 136 on at least one allele with 77% homozygous (VV136) and 23% valine/alanine heterozygotes (VA136). Mean survival time was 907 and 1482 days for VV136 and VA136 scrapie affected animals respectively. VV136 animals were all at great risk of disease if allowed to live long enough. However scrapie occurred only in a specific subgroup of VA136 sheep, survival advantage depending on VA136 animals being heterozygous for other polymorphisms at codons 154 or 171. The flock history has been recorded in great detail since its foundation in 1960 however there was no strong evidence for simple maternal or paternal transmission of disease other than inheritance of PrP genotype.

Glycoinositol phospholipid anchor and protein C-terminus of bovine erythrocyte acetylcholinesterase: analysis by mass spectrometry and by protein and DNA sequencing

Purified bovine erythrocyte acetylcholinesterase (AChE) was radiomethylated on its amine groups and incubated with bacterial phosphatidylinositol-specific phospholipase C to remove the lipid portion of the AChE glycoinositol phospholipid (GPI) anchor, and a C-terminal tryptic fragment that contained the residual GPI glycan was isolated by HPLC. Analysis by electrospray-ionization mass spectrometry revealed a parent ion of m/z 3798. The fragmentation patterns produced by collision-induced dissociation mass spectrometry of the +4 and +5 states of the parent ion indicated a 23-amino acid peptide in amide linkage to ethanolamine-P04-Hex-Hex-Hex(PO4-ethanolamine)(HexNAc)-Hex N(Me)2-inositol phosphate. The glycan structure is completely consistent with that obtained previously for the GPI anchor of human erythrocyte AChE except for the addition of the HexNAc substituent. A nearly complete peptide sequence was deduced from the fragmentation patterns, although four assignments were based only on single fragments of very low abundance. To resolve this uncertainty, a segment of bovine genomic DNA corresponding to the C-terminal AChE sequence was amplified by PCR. DNA sequencing established the 23-amino acid peptide sequence to be FLPKLLSATASEAPCTCSGPAHG, in agreement with the MS data and consistent with results from Edman protein sequencing. Dimerization of AChE polypeptides is mediated by intersubunit disulphide bonding in this C-terminal segment, but the bovine AChE contained two cysteine residues in a ...CTC... motif, in contrast with human AChE which contains only a single cysteine in this segment. Although bovine AChE contained no free thiol groups reactive with iodo[14C]acetamide, partial reduction and alkylation with iodo[14C]acetamide revealed that conversion into monomers occurred with an overall incorporation of only one alkyl group per monomer. An identical level of alkylation was observed when dimeric human AChE was converted into monomers by partial reduction. The question of whether the bovine AChE contains one or two intersubunit disulphide linkages is considered.

Health risk factors and health promoting behavior of medical, dental and nursing students

The assumption of this study is: the preventive care beliefs and practices of health science students stand-out among the general public. To test this assumption, a survey of beliefs, behaviors and disease prevention practices of medical, dental, undergraduate and graduate nursing students in three health science schools was carried out in New Jersey. All students in these three schools were included in the study. A questionnaire which consisted of information on socio-demographic, life style patterns, health risk factors, and preventive cares was used. Results showed that 99% of the students knew their blood pressure, 10% were cigarette smokers and 3% were heavy drinkers. Approximately 68% of the students exercised regularly and 78% of them used seat belts. About 81 and 79% of the female students had regular clinical breast examinations (CBE) and pelvic examinations, respectively. It is worth noting that 10% of medical and dental students had driven an automobile under the influence of alcohol. About 77% of all students did not know their cholesterol levels, and 14% of dental students reported no concern about fat consumption. Only 38% of the female students reported monthly breast self examination (BSE). Over 27% of undergraduate nursing and 14% of all students never had a Papanicolaou (Pap) test. The main reasons for never having a Pap test, CBE, and pelvic examinations were: they did not think it was necessary and they believed that they were not at risk. The major reason for not performing BSE was forgetfulness.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunohistochemical localization of GABAA receptors in the mammalian crista ampullaris

The distribution of GABAA receptor-like immunoreactivity in the hamster, rat, and mouse crista ampullaris was determined by use of a monoclonal antibody to the beta 2 and beta 3 subunits of the GABAA receptor. In the crista ampullaris, punctate staining was seen associated with the calyces surrounding vestibular type I hair cells. Afferent nerve fibers approaching the hair cell layer were often observed to be immunoreactive. Hair cells, supporting cells, and cells in the transitional and dark cell regions were not immunoreactive. The distribution of staining of calyces appeared to be relatively uniform in all regions (crest and slope) of the crista. In addition, cell bodies located in the vestibular ganglion were immunoreactive. The association of GABAA receptor-like immunoreactivity with the afferent nerve calyx and cell body of the vestibular ganglion cells suggests that GABA may act to modify afferent nerve transmission at the calyceal afferent nerve ending.

Time-dependent inhibition of glucose 6-phosphatase by 3-mercaptopicolinic acid

3-Mercaptopicolinate (3-MP) inhibits D-glucose-6-phosphate (G6P) phosphohydrolase activity of the glucose-6-phosphatase system (Bode et al. (1993) Biochem. Cell Biol. 71, 113-121). We therefore attempted to maximize the inhibition by varying the physical state of microsomes, the concentration of 3-MP, and the time of preliminary incubation of 3-MP with the enzyme. The inhibition was irreversible and time- and inhibitor-concentration-dependent, with G6P phosphohydrolase activity of intact rat liver microsomes, but there was no inhibition with detergent-treated microsomes. The effectiveness of 3-MP as a time-dependent inhibitor of glucose 6-phosphatase was demonstrated in situ by measuring glycogenolysis in isolated, perfused livers from fed rats. We first exposed the livers to 2 mM 3-MP for 40 min, and then assessed the inhibitory effects on glycogenolysis. It was lowered by 50%. These observations establish that 3-MP at the mM level may be useful as an experimental probe in the study of the role(s) of G6P in the regulation of glycogenolysis as well as glycogenesis. Further, they validate the use of much lower (microM) concentrations of 3-MP to block gluconeogenesis (at the phosphoenolpyruvate carboxykinase step) without interfering with glucose 6-phosphatase. We also explored the mechanism of 3-MP inhibition. The time-dependent inhibition of carbamoyl-phosphate:glucose phosphotransferase activity with microsomes incubated with 1 mM 3-MP for 60 or 90 min and then assayed with 1 mM carbamoyl phosphate and 180 mM glucose was modest compared with inhibition of G6P phosphohydrolase. When G6P production by carbamoyl-phosphate:glucose phosphotransferase was reduced by decreasing glucose concentration to 60 mM, no inhibition by 3-MP was discernible. There was no inhibition of inorganic pyrophosphatase activity. These studies support the model of time-dependent, irreversible reaction of 3-MP with the G6P translocase component of the glucose-6-phosphatase system.

Immunohistochemical localization of S-100 protein in auditory and vestibular end organs of the mouse and hamster

The distribution of S-100-like immunoreactivity in mouse and hamster auditory and vestibular end organs was determined by the use of immunohistochemistry. Within the organ of Corti, the cytoplasm of cells of Deiter and Hensen were strongly immunoreactive. Inner hair cells and the peripheral processes and cell bodies of the spiral ganglion were weakly immunoreactive for S-100, whereas the supranuclear regions of outer hair cells and cells underlying the basilar membrane were unstained. Immunoreactivity was observed near the base of outer hair cells. In the lateral wall of the cochlea, cellular components of the spiral ligament and a subpopulation of epithelial cells in the stria vascularis, identified as predominantly basal cells, were immunoreactive. For the saccule, utricle, and semicircular canals, S-100 immunoreactivity was observed in vestibular hair cells, types I and II, and the nerve calyces surrounding type I hair cells as well as in nerve fibers underlying the sensory epithelium. Weak S-100-like immunoreactivity was associated with vestibular nerve fibers and cell bodies in the vestibular ganglion. The localization of S-100-like immunoreactivity to the sensory cells and nerve fibers of the peripheral auditory and vestibular end organs is consistent with a functional role for S-100 proteins at these sites.

Glycogenesis from glucose and ureagenesis in isolated perfused rat livers. Influence of ammonium ion, norvaline, and ethoxyzolamide

The probable involvement of hepatic carbamyl-P in the reciprocal relationship between hepatic ureagenesis and glycogenesis from glucose was explored. Isolated perfused liver preparations from 48-h fasted rats were employed. Moderate (9.2 mM) and relatively high levels of glucose (34 mM) were perfused. Hepatic glycogenesis, glucose-6-P, carbamyl-P, and citrulline levels, hepatic urea formation, and ureagenesis based upon perfusate urea levels were measured. Experimental probes selected to modify hepatic ureagenesis and carbamyl-P production and utilization included: (a) NH4Cl, maintained at 5 mM by continuous infusion (NH4+ is a substrate for carbamyl-P synthase I and glutamate dehydrogenase); (b) norvaline, an inhibitor of ornithine transcarbamylase which catalyzes the first committed step in the urea cycle; and (c) ethoxyzolamide, an inhibitor of carbonic anhydrase which produces HCO3-, an essential substrate for carbamyl-P synthase I. NH4+ increased ureagenesis and decreased glycogenesis. The inclusion of norvaline with NH4+ decreased ureagenesis and increased glycogenesis. Ethoxyzolamide with or without NH4+ inhibited both ureagenesis and glycogenesis, and decreased the hepatic glucose-6-P level. Glycogenesis was greater at 34 mM than 9.2 mM glucose, increased in norvaline-containing preparations correlative with increased availability of carbamyl-P, and decreased when carbamyl-P formation was inhibited by ethoxyzolamide. Kinetic analysis indicated a Km, Glc of 31 mM for glucose phosphorylation preliminary to glycogenesis. Glycogen formation via the "indirect pathway" (i.e. involving extrahepatic glycolysis, transport of lactate to the liver, and glyconeogenesis therefrom) was quantitatively insufficient to account for the observed glycogenesis. Glucokinase is contraindicated by the inverse relationship between hepatic glycogenesis and ATP availability in the ethoxyzolamide-treated preparations. In contrast, carbamyl-P:glucose phosphotransferase activity of the glucose-6-phosphatase system has the characteristics to bridge hepatic ureagenesis and glycogenesis.

Transmission of bovine spongiform encephalopathy to sheep and goats

Spongiform encephalopathy has been confirmed in both 'positive' and 'negative' lines of Cheviot sheep (selected for their differential response on experimental exposure to scrapie) after intracerebral injection or oral dosing with brain homogenate derived from cattle with bovine spongiform encephalopathy (BSE). With either challenge the incubation period of the disease ranged from 440 to 994 days in both lines of sheep. In a similar experiment, three Anglo-Nubian goats developed the disease 506 to 570 days after intracerebral infection with the same BSE homogenate, and two of three goats developed the disease 941 and 1501 days after oral dosing; the other goat and some sheep from each of the experimental groups remain alive 1720 days after exposure. This is the first report of the experimental transmission of BSE to sheep and goats.

Immunohistochemical localization of S-100 protein in the saccule of the rainbow trout (Salmo gairdnerii R.)

The distribution of S-100-like immunoreactivity in the trout saccule (a presumed organ of hearing in fish) has been determined by means of immunohistochemistry. Within the sensory epithelium of the saccular macula, hair cells and myelinated saccular nerve fibers were found to be immunoreactive. Hair-cell immunoreactivity was relatively uniform throughout the macula except at the extreme periphery (rostral, caudal, ventral and dorsal), where staining was either decreased or absent. The immunoreactivity associated with myelinated nerve fibers was greatest at the peripheral edges of the nerve processes, a position corresponding to the location of Schwann cells. However, the nerve processes themselves (within and subjacent to the sensory epithelium), as well as cell bodies within the saccular nerve, were also immunoreactive. Thus, the immunoreactivity of the saccular nerve observed above the basal lamina can be attributed to the saccular nerve processes as well as to nerve-associated Schwann cells. Overall, the immunoreactivity displayed by hair cells was less intense than that associated with myelinated saccular nerve, as evidenced by a disappearance of signal in hair cells first, upon serial dilution of antibody. No S-100-like immunoreactivity was observed in supporting cells within the sensory epithelium or in epithelial cells in non-sensory regions. A concentration of S-100-like immunoreactivity in hair cells and saccular nerve is suggestive of the presence of S-100 calcium-binding protein-mediated activities in these cell types.

Swaledale sheep affected by natural scrapie differ significantly in PrP genotype frequencies from healthy sheep and those selected for reduced incidence of scrapie

PrP glycoprotein gene polymorphisms were examined in Swaledale sheep affected by natural scrapie, in healthy sheep and in Swaledales selected for low susceptibility to scrapie. The three groups differed significantly in frequencies of PrP genotypes detected by the restriction enzymes EcoRI, HindIII and BspHI, the latter being indicative of a PrP protein amino acid difference at codon 136. These frequency differences were confirmed in a single-flock study and present good evidence that scrapie susceptibility and resistance are associated with PrP gene variants in Swaledale sheep.

Conjunctival instillation of scrapie in mice can produce disease

Mice were infected with one of two strains of scrapie by instilling brain homogenate into the conjunctiva to establish whether infection could be initiated. Of the 55 mice infected with ME7 scrapie, 23 developed clinical disease 323 +/- 8 (mean +/- standard error) days later. Three out of 12 mice infected with 79A scrapie developed disease after 232 +/- 35 days. The ME7 incubation period is similar to that for the oral route of infection. We feel that these results emphasize the need for adequate eye protection when handling tissues infected with spongiform encephalopathies.

Inhibition of glucose-6-phosphate phosphohydrolase by 3-mercaptopicolinate and two analogs is metabolically directive

3-Mercaptopicolinae (3-MP) blocks gluconeogenesis from lactate, pyruvate, alanine, and other substrates through its inhibition of phosphoenolpyruvate carboxykinase. Nevertheless, we observed increased glycogenesis, net glucose uptake, and glucose-6-P levels in livers perfused with glucose in the presence of 3-MP. In perfusions with 20 mM dihydroxyacetone, increased glycogenesis and decreased glucose production were observed with 3-MP. These metabolic effects suggested additional site(s) of action of 3-MP. Further studies showed that 3-MP inhibits glucose-6-P phosphohydrolase activity of intact liver microsomes. Several compounds with structural similarities to 3-MP (2-mercaptonicotinic acid, picolinic acid, cysteine, reduced glutathione, nicotinic acid, quinolinic acid, tryptophan, and pyridine) were tested for their effect on glucose-6-P phosphohydrolase activity. Two of these compounds, 2-mercaptonicotinic acid and picolinic acid, were found to inhibit. In perfusions including 7.5 mM fructose, the addition of 3-MP, 2-mercaptonicotinic acid, or picolinic acid increased glycogenesis, decreased glucose production, and increased hepatic glucose-6-P concentrations. These observations indicate that the inhibition of glucose-6-P phosphohydrolase may play a role in enhanced glycogenesis from glucose, dihydroxyacetone, and fructose in isolated livers from 48-h fasted rats perfused with 3-MP or certain sulfhydryl-containing and sulfhydryl-devoid analogs.

Cervical cancer and health care resources in Newark, New Jersey, 1970 to 1988

OBJECTIVES

In the past, the predominantly Black population of Newark, NJ, had little access to programs promoting or providing Pap tests. The ratio of in situ to invasive cases of cervical carcinoma was markedly reduced in all age categories, indicating inadequate screening for this cancer in this population. Funding became available to provide and publicize Pap smears but ceased after 5.5 years. We examined the effect of these changes in funding.

METHODS

Data came from all Newark hospitals and practitioners and from the state cancer registry. There are now data on incidence of in situ and invasive cervical cancer in Newark from 1970 through 1988, including years before, during, and after program funding.

RESULTS

The ratio of in situ to invasive cervical cancer increased and decreased in a striking parallel with the provision and subsequent cessation of funding.

CONCLUSIONS

Cessation of funding of education and screening programs can result in resumption of an unfavorable in situ/invasive cervical carcinoma ratio in a poor population.

Cellular events involved in hormonal control of receptor-mediated endocytosis: regulation occurs at multiple sites in the low density lipoprotein pathway, including steps beyond the receptor

We used biochemical and quantitative structural approaches to analyze hormonal regulation of receptor-mediated endocytosis of human low density lipoprotein (LDL) by differentiating rat granulosa cells in culture. We studied uptake and metabolism of 125I-labeled LDL and distribution of gold-labeled LDL in nontreated and FSH- or FSH/androstenedione-treated granulosa cells. FSH and androstenedione worked together to enlarge the segment of the granulosa cell population capable of accumulating LDL and to increase the number of LDL receptors at the cell surface. More importantly, FSH affected postreceptor aspects of the LDL pathway, including 1) accelerating the apparent rate of LDL internalization, and 2) decreasing the time needed for LDL to reach lysosomes. In both cases we eliminated the possibility that the observed effects merely reflected differences in receptor numbers between hormone-treated and nontreated cells. FSH also increased the number of both gold-labeled lysosomes per cellular profile and gold particles per lysosome. In all, FSH expanded the capacity of the LDL pathway to accommodate more intracellular ligand by augmenting the numbers of organelles participating in the endocytic process. However, it did not affect cell size, sizes of individual organelles comprising the LDL pathway, or numbers of gold particles per organelle (except lysosomes). Our findings indicate that hormonal regulation of the LDL pathway extends beyond simply causing expression of cell surface LDL receptors to encompass postreceptor events, including enhancing the apparent rates at which ligand is internalized and transported to lysosomes.

Natural scrapie in British sheep: breeds, ages and PrP gene polymorphisms

One hundred and sixty-seven sheep of 32 breeds and crossbreeds affected by natural scrapie throughout Britain were tested for the presence of restriction fragment length polymorphisms of the PrP gene observed when their DNA was digested with EcoRI or HindIII. These polymorphisms have already been associated with different susceptibilities to experimental scrapie (controlled by alleles of the Sip gene) in a flock of Cheviot sheep. In two studies 86 to 92 per cent of the sheep were found to carry the PrP gene EcoRI fragment e1 which is associated with high susceptibility (or the sA allele of Sip) to experimental scrapie. The PrP gene HindIII genotypes of the natural scrapie sheep were not apparently associated with differences in susceptibility to scrapie. There was no link between the polymorphisms and the age or breed of the affected sheep.

Studies on maternal transmission of scrapie in sheep by embryo transfer

The technique of embryo transfer was used to investigate the maternal transmission of scrapie in sheep. Embryo donor ewes were experimentally infected with scrapie (all eventually developing the disease) and artificially inseminated six months later with semen from an uninfected scrapie-susceptible ram. Embryos were harvested five and six days after insemination and transferred by laparoscopy, unwashed, into recipient ewes which had been genetically selected for very low susceptibility to scrapie. Six of the 26 lambs born to these recipients developed scrapie.

Glyconeogenesis from L-proline involves metabolite inhibition of the glucose-6-phosphatase system

L-Proline's glycogenic action is unlike that of other amino acids in that it produces effects beyond those explainable by a simple increase in osmolarity (Baquet, A., Hue, L., Meijer, A. J., van Woerkom, G. M., and Plomp, P. J. A. M. (1990) J. Biol. Chem. 265, 955-959). We postulate that this effect may relate to inhibition of hepatic glucose-6-P hydrolysis by a proline-derived metabolite. We tested this hypothesis with isolated livers from rats fasted 48 h which were perfused with L-proline or L-glutamine. Net glucose and net glycogen production and levels of glucose-6-P and certain other hepatic metabolites were measured. The data obtained support our hypothesis by demonstrating fundamental differences in the metabolic fates of proline and glutamine in the liver. Both pass through alpha-ketoglutarate in the initial stage of gluconeogenesis, but proline supports hepatic glycogen formation while glutamine does not. The concomitant increase in hepatic glucose-6-P and proline-associated glyconeogenesis suggests that inhibition of glucose-6-P hydrolysis by a proline-derived metabolite may divert glucose-6-P produced from proline from glucose production and to glycogen synthesis. This conclusion is supported by the effects of perfusions with and without proline (3-mercaptopicolinate present) on (a) glyconeogenesis and glucose formation from dihydroxyacetone, (b) net glucose uptake and glycogen formation with 30 mM glucose as substrate, and (c) glucose production from endogenous glycogen in perfused livers from fed rats.

Ultrastructural localization of sialylated glycoconjugates in cells of the salamander olfactory mucosa using lectin cytochemistry

An indirect gold-labeling method utilizing the lectin from Limax flavus was employed to characterize the subcellular distribution of sialic acid in glycoconjugates of the salamander olfactory mucosa. The highest density of lectin binding sites was in secretory vesicles of sustentacular cells. Significantly lower densities of lectin binding sites were found in secretory granules of acinar cells of both Bowman's and respiratory glands. Lectin binding in acinar cells of Bowman's glands was confined primarily to electron-lucent regions and membranes of secretory granules. In the olfactory mucus, the density of lectin binding sites was greater in the region of mucus closest to the nasal cavity than in that closest to the epithelial surface. At the epithelial surface, the density of lectin binding sites associated with olfactory cilia was 2.4-fold greater than that associated with microvilli of sustentacular cells or non-ciliary plasma membranes of olfactory receptor neurons, and 7.9-fold greater than non-microvillar sustentacular cell plasma membranes. Lectin binding sites were primarily associated with the glycocalyx of olfactory receptor cilia. The cilia on cells in the respiratory epithelium contained few lectin binding sites. Thus, sialylated glycoconjugates secreted by sustentacular cells are preferentially localized in the glycocalyx of the cilia of olfactory receptor neurons.