Localization of metallothionein in female reproductive organs of rat and guinea pig

We demonstrated the localization of metallothionein (MT) in rat uterus and ovaries and in guinea pig mammary glands. During the cyclic changes from one estrous period to the next, strong MT immunostaining was found in the glandular epithelium of the endometrium and weak immunostaining was observed in the simple columnar epithelium. Interestingly, during estrus, the intensity of MT immunostaining decreased in the cytoplasm, whereas during metestrus, diestrus, and proestrus the intensity of strong and similar immunostaining was observed in both the cytoplasm and nucleus. During proestrus and estrus, the number of vaginal epithelial cells containing MT increased on the luminal side of the epithelium and inside the lumen. In rat ovary, strong immunostaining was observed in the cytoplasm and nucleus of granulosa-lutein cells of the corpus luteum and in the cytoplasm of the ovum. In mammary gland of non-pregnant guinea pig, very strong but scattered MT immunostaining was demonstrated in both cytoplasm and nucleus of some epithelial cells of the lactiferous ducts. The mammary tissue of the pregnant guinea pig showed an increase in MT staining in alveolar cells that had proliferated due to pregnancy. The presence of MT in the female reproductive organs, the tissues of which actively grow under the control of female sex hormones, indicates some as yet unknown association of MT with cell proliferation and differentiation.     

Study on the variables affecting toxicity of hybrid toxins. The effect of different target cell receptor distribution and toxin binding chain

Disulfide conjugates of diphtheria toxin (DT) and its fragment A (DTA) to asialoorosomucoid (ASOR) were prepared. The toxicity of the conjugates were compared with DT in isolated rat, rabbit and guinea pig hepatocytes containing different concentration of asialoglycoprotein receptors (Biochim. Biophys, Acta 942, 57, 1988). In rat hepatocytes DTA-ASOR was highly toxic with half-maximal inhibitory concentration (IC50) of protein synthesis occurring at 4 +/- 3.10(-11) M (n = 7) which was much lower than that of DT DT (7.8 +/- 9.8.10(-9) M, n = 7). In rabbit hepatocytes toxicity of the conjugate (IC50 = 5.4 +/- 4.9.10(-10) M, n = 7) was higher than that of DT (IC50 = 5 +/- 4.10(-11) M, n = 7). In guinea pig hepatocytes, DTA-ASOR was not toxic at concentration below 10(-8) M, although DT was highly toxic (IC50 = 1.8 +/- 1.4.10(-10), n = 3). In the presence of 5 microM colchicine, the toxicity of DTA-ASOR in rat and rabbit hepatocytes increased by 10-fold, while in guinea pig hepatocytes it became detectable with an IC50 of 1.2 +/- 0.8.10(-9) M (n = 3). The toxicity of DT in the rat cells was also enhanced 10-fold by colchicine, but not at all in either the rabbit or the guinea pig cells. Addition of isolated diphtheria toxin fragment B (DTB) did not affect significantly the toxicity of DTA-ASOR in all three hepatocytes and that of DT in rat hepatocytes, but reduced toxicity of DT more than 20-fold in the rabbit and guinea pig cells. Toxicity of DT-ASOR in rat hepatocytes was the same as DTA-ASOR both in the absence and presence of colchicine, and abolished completely by excess ASOR, but not by DTB. Toxicity of DT-ASOR in rabbit hepatocytes was 40-times higher than DTA-ASOR, enhanced 10-fold by cochicine and reduced more than 30-fold by excess ASOR, but only slightly by DTB. These results indicate that entry of DTA from DTA-ASOR involve a DTB-independent translocation mechanism which can be as efficient as the DTB-dependent mechanism used by DT in the rabbit and guinea pig cells. The entry of both conjugates appeared to be mediated by the asialoglycoprotein receptors. However, the DTB moiety of DT-ASOR could function only in the DT-sensitive cells indicating the lack of a DTB-mediated translocation in the DT-resistant cells.     

Rosette formation between rat thymocytes and guinea pig erythrocytes requires "active" fetal calf serum. I. Characteristics of "active" serum factors and receptors on thymocytes and erythrocytes.

Rosette formation between rat thymocytes and guinea pig erythrocytes is dependent on at least two factors present in non-heat treated fetal calf serum. One factor is a high molecular weight, heat stable substance and the other factor is a heat labile substance(s). The rosette formation process is divalent cation dependent and seems to involve the sequential binding to thymocytes of the high molecular weight, heat stable substance, the heat labile substance (s), and then guinea pig erythrocytes. Thymocytes appear to bear a receptor which is dependent on hexose monophosphate shunt metabolism, is not removed by many digestive enzymes, but is blocked with phytohemag-glutinin and pokeweed mitogen. Erythrocytes appear to bear a receptor which is dependent on hexose monophosphate shunt metabolism, removed by pronase treatment, and blocked by phytohemagglutinin and concanavalin A.     

Chromatofocusing of mammalian estrone sulfate sulfohydrolase activity

Estrone sulfate sulfohydrolase (estrogen sulfatase) activity was solubilized by treatment with Triton X-100 from 105,000 g pellets of guinea pig uterus, testis and brain, as well as from rat liver and human placenta. The solubilized forms were subjected to chromatofocusing in the fast protein liquid chromatography (FPLC) system and on conventional columns packed in our laboratory. The guinea pig tissue pattern was complex. Uterus showed peaks of activity with apparent pI's of 9.11 and 7.6; testis contained 3 peaks with pI's of 9.18, 8.7 and 7.5; brain possessed peaks with pI's of 9.28 and 8.6. In each case the major activity peak was that with pI greater than 9. Rat liver activity chromatofocused as a single peak of apparent pI = 6.87 and the human placental enzyme also showed a single, though broad, peak, of pI = 6.57. This suggests not only that the guinea pig enzyme(s) differs markedly from those of rat liver and human placenta, but that there may be qualitative differences between the forms in the three guinea pig tissues. Chromatofocusing behaviour was not independent of the specific exchange resins and ampholytes utilized. The recovered enzyme activity was fairly stable and it seems that chromatofocusing could be a useful step in purification of the guinea pig enzyme(s), particularly the main form possessing a pI greater than 9.     

Further evidence for non-pancreatic insulin immunoreactivity in guinea pig brain

The existence of large amounts of insulin in rat brain and of a porcine- or rat-like insulin in guinea pig brain have been disputed on the basis of differing results from standard (Method I) and hydrophobic adsorption techniques (Method II) for concentrating insulin from acid ethanol extracts. To try to resolve these differences, acid ethanol extracts of rat and guinea pig brains were divided into equal aliquots and concentrated for insulin radioimmunoassay (RIA) by both techniques. The RIA used guinea pig anti-porcine insulin serum, with 50% B0 for purified pancreatic porcine, rat and guinea pig insulin standards being 1.35, 2.38 and greater than 1,000 ng/ml, respectively. Oral glucose (4 g/kg) produced plasma glucose of 377 mg/dl in a guinea pig by 20 min but was not associated with any porcine- or rat-like immunoreactive insulin. Dilutions of guinea pig and rat brain extracts had parallel cross-reactivity with insulin standard curves. Insulin contents of rat brain (uncorrected for recovery) against porcine and rat insulin standards, respectively, were 1.33 and 1.93 ng/g (Method I) and 5.93 and 11.67 ng/g (Method II). Rat plasma was 0.85 and 1.42 ng/ml, respectively. Guinea pig contained 1.35 and 1.89 ng/g (uncorrected), respectively (Method I), and 2.99 and 5.62 ng/g, respectively (Method II). Guinea pig plasma was below the sensitivity of the RIA (less than 0.15 ng/ml). These results suggest that a porcine- or rat-like insulin may exist in guinea pig brain.     

Estrone sulfate sulfohydrolase in the developing brain and pituitary of rat, mouse and guinea pig

The pattern of estrone sulfate sulfohydrolase (estrogen sulfatase) development in the brain of rat, mouse and guinea pig has been established by assaying whole homogenates. Activity was measurable in each species from the fetal state to adulthood. Maximum brain content was reached at about 20 days of age in rat, 14 days in mouse and 15 days in guinea pig. A considerable decrease occurred between 14 days and adulthood in mouse and lesser decreases were seen in rat and guinea pig. The subcellular distribution of enzyme in rat and mouse brain appeared to change from the immature to the adult state. No major differences in enzyme activity occurred between the sexes at any age. Tissue concentration of enzyme in the hypothalamic-preoptic area of rat and mouse was similar to that in the remainder of the brain. In guinea pig the brain concentration was slightly lower than that of the hypothalamic-preoptic region. Sulfatase content of the pituitary was low in all 3 species but the tissue concentration was considerably higher than that of brain, particularly in rat and mouse. Apparent Km values for brain sulfatase were in the range 6-17 microM, with no striking sex difference. Apparent Km's for pituitary sulfatase of immature rat and guinea pig were similar to those for brain in the same animals but that for mouse pituitary (0.9 microM) was much lower. It is unlikely that brain or pituitary sulfatase is by itself, a major factor in making available potentially active estrogen for use during differential sex development in these species.     

Relationship between 5-HT2A receptor mRNA density and contractility in trachea and aorta from guinea pig and rat

The present studies document marked differences in contractile responsiveness to serotonin in trachea and aorta between guinea pig and rat. For example, the guinea pig trachea and rat aorta markedly contract in response to serotonin via activation of 5-HT_2A receptors. In contrast, the rat and guinea pig aorta only modestly contract to serotonin. The availability of 5-HT_2A receptor selective cDNA clones from brain of both guinea pig and rat permitted molecular probes to be designed and PCR amplification studies initiated to identify and quantify 5-HT_2A receptor specific mRNA in these tissues. For trachea, 3-fold higher concentrations of 5-HT_2A receptor specific mRNA were found in guinea pig relative to rat trachea. These data are consistent with the more profound contractile response to serotonin in guinea pig versus rat trachea and suggest that differences in tracheal contractility to serotonin correlate with the density of 5-HT_2A receptor mRNA. In contrast, although rat aorta contracted more dramatically to serotonin than guinea pig aorta, rat aorta possessed a similar concentration of 5-HT_2A receptor specific mRNA as compared to guinea pig aorta. Thus, for the aorta, differences in the concentration of 5-HT_2A receptor mRNA are not sufficient to explain the observed differences in contractility between tissues from guinea pig and rat. These studies documenting 5-HT_2A receptor mRNA in rat trachea and guinea pig aorta, two tissues that do not markedly contract in response to serotonin indicate that 5-HT_2A receptor mRNA although present, has not resulted in a receptor capable of mediating a contractile response in these tissues.     

Species Differences in the Brain Regional Distribution of Receptor Binding for Thyrotropin-Releasing Hormone

Abstract: A survey of the regional distribution of binding of 1 nM [³H](3-MeHis²)thyrotropin-releasing hormone ([³H]MeTRH) to TRH receptors in the brains of eight mammalian species revealed major species differences in both the absolute and relative values of TRH receptor binding in different brain regions. Several brain regions exhibited binding equal to or exceeding that in the anterior pituitary gland of the same species, including the amygdaia in the guinea pig and rat, the hypothalamus in the guinea pig, the nucleus accumbens in the rabbit, and all these and other regions in the cat and dog, for which pituitary binding was exceptionally low. Species could be divided into two groups according to which brain region appeared highest in binding: rabbits, sheep, and cattle had highest binding in the nucleus accumbens/septal area, whereas guinea pigs, rats, dogs, cats, and pigs had highest binding in the amygdala/temporal cortex area. The nucleus accumbens consistently exceeded the caudate-putamen in receptor binding. For most brain regions, rabbits, rodents, and sheep tended to be higher than carnivores, cattle, or pigs. Further regions that exhibited appreciable binding in most species included the olfactory bulb and tubercle, hippocampus, and various cortical and brain stem areas. In fact, essentially all brain regions appeared to have detectable levels of TRH receptors in at least some species, but no rat peripheral tissues have yet shown detectable receptor binding. The species differences appeared to reflect largely if not entirely differences in receptor density, although this was not tested in every species.     

Synthesis of (pGlu-5, MePhe-8, Sar-9) substance P (5-11) (DiMe-C7) using a polyacrylamide resin and biological activity on guinea pig ileum and tracheal smooth muscle

DiMe-C7 (pGlu-Gln-Phe-MePhe-MeGly-Leu-MetNH2), a metabolically stable analogue of Substance P, was prepared by solid-phase peptide synthesis using a polyacrylamide resin and a labile anchorage derived from glycolic acid. Myotropic activities in guinea pig ileum (ED50 = 4.0 +/- 1.5 10(-8) M) and guinea pig trachea (ED50 = 8.6 +/- 3.5 10(-8) M) are discussed in comparison with the corresponding activities of Substance P.     

Increased sensitivity of the enzymatic isotopic assay of histamine: measurement of histamine in plasma and serum.

The use of rat kidney instead of guinea pig brain as the source of histamine-N-methyltransferase for the enzymatic assay of histamine was found to improve the sensitivity of the assay. A partially purified preparation (ammonium sulfate fractionation) of the kidney enzyme was 20- to 50-fold more active than the guinea pig preparation, and sufficient enzyme for 14,000 assays could be prepared from six rats. The kidney enzyme, unlike the guinea pig brain enzyme, was free of interfering enzyme activities and gave low values for assay blanks. The two enzymes otherwise had similar properties. The low blank values permitted direct measurement of histamine in normal plasma without the need to isolate and concentrate histamine from the sample. Plasma histamine levels in normal individuals ranged from 0.2-1.4 (mean 0.6, n = 19) ng/ml.     

Microtubule assembly in developing mammalian brain.

Microtubule protein was measured in mouse brain homogenates by quantitative colchicine binding. Neonatal animals contained more than twice the amount of brain tubulin as adult mice. The percentage of colchicine-binding protein which was polymerized was determined by extracting brain at room temperature into a medium designed to stabilize intact microtubules. Under identical conditions and tubulin concentrations, neonatal brain tubulin (colchicine-binding activity) had a greater proportion of the total extracted in an apparently polymerized state (pelletable by centrifugation) than did adult brain. A slight variation in the ratio of assembled to unassembled tubulin was observed with varying protein concentration (volume of extract), indicating that the values obtained may not reflect exactly the in vivo situation, because a rapid equilibration takes place upon homogenization. At all protein concentrations, the neonatal brain extracts contained a significantly greater proportion of assembled tubulin than did adult brain. This proportion began to fall at 5 days postnatal and reached the adult level at 30 days. The tubulin assembled/not assembled ratios were not altered by addition of nucleoside triphosphates, additional EGTA, or sulfhydryl protecting agents, and did not vary with preparation times of 30–90 min. The colchicine-binding reaction and decay of colchicine-binding activity with time were similar in extracts of different aged mouse brains, with neonatal slightly more stable than adult. Pools of tubulin from any age which were soluble at room temperature (unpolymerized) could not repolymerize well in vitro when incubated with GTP at 37 °C, whereas pools of tubulin which were sedimentable at room temperature (polymerized) could be redissolved at 0 °C and readily reassembled at 37 °C. The neonatal extract tubulin was thus more polymerization competent than the adult extracts; this correlates with a greater proportion of assembled tubulin in extracts at room temperature and possibly in vivo.     

Individual microtubules in the axon consist of domains that differ in both composition and stability

We have explored the composition and stability properties of individual microtubules (MTs) in the axons of cultured sympathetic neurons. Using morphometric means to quantify the MT mass remaining in axons after various times in 2 micrograms/ml nocodazole, we observed that approximately 48% of the MT mass in the axon is labile, depolymerizing with a t1/2 of approximately 5 min, whereas the remaining 52% of the MT mass is stable, depolymerizing with a t1/2 of approximately 240 min. Immunofluorescence analyses show that the labile MTs in the axon are rich in tyrosinated alpha-tubulin, whereas the stable MTs contain little or no tyrosinated alpha-tubulin and are instead rich in posttranslationally detyrosinated and acetylated alpha-tubulin. These results were confirmed quantitatively by immunoelectron microscopic analyses of the distribution of tyrosinated alpha-tubulin among axonal MTs. Individual MT profiles were typically either uniformly labeled for tyrosinated alpha-tubulin all along their length, or were completely unlabeled. Roughly 48% of the MT mass was tyrosinated, approximately 52% was detyrosinated, and approximately 85% of the tyrosinated MTs were depleted within 15 min of nocodazole treatment. Thus, the proportion of MT profiles that were either tyrosinated or detyrosinated corresponded precisely with the proportion of MTs that were either labile or stable respectively. We also observed MT profiles that were densely labeled for tyrosinated alpha-tubulin at one end but completely unlabeled at the other end. In all of these latter cases, the tyrosinated, and therefore labile domain, was situated at the plus end of the MT, whereas the detyrosinated, and therefore stable domain was situated at the minus end of the MT, and in each case there was an abrupt transition between the two domains. Based on the frequency with which these latter MT profiles were observed, we estimate that minimally 40% of the MTs in the axon are composite, consisting of a stable detyrosinated domain in direct continuity with a labile tyrosinated domain. The extreme drug sensitivity of the labile domains suggests that they are very dynamic, turning over rapidly within the axon. The direct continuity between the labile and stable domains indicates that labile MTs assemble directly from stable MTs. We propose that stable MTs act as MT nucleating structures that spatially regulate MT dynamics in the axon.     

Microtubule-associated proteins-dependent colchicine stability of acetylated cold-labile brain microtubules from the Atlantic cod, Gadus morhua

Assembly of brain microtubule proteins isolated from the Atlantic cod, Gadus morhua, was found to be much less sensitive to colchicine than assembly of bovine brain microtubules, which was completely inhibited by low colchicine concentrations (10 microM). The degree of disassembly by colchicine was also less for cod microtubules. The lack of colchicine effect was not caused by a lower affinity of colchicine to cod tubulin, as colchicine bound to cod tubulin with a dissociation constant, Kd, and a binding ratio close to that of bovine tubulin. Cod brain tubulin was highly acetylated and mainly detyrosinated, as opposed to bovine tubulin. When cod tubulin, purified by means of phosphocellulose chromatography, was assembled by addition of DMSO in the absence of microtubule-associated proteins (MAPs), the microtubules became sensitive to low concentrations of colchicine. They were, however, slightly more stable to disassembly, indicating that posttranslational modifications induce a somewhat increased stability to colchicine. The stability was mainly MAPs dependent, as it increased markedly in the presence of MAPs. The stability was not caused by an extremely large amount of cod MAPs, since there were slightly less MAPs in cod than in bovine microtubules. When "hybrid" microtubules were assembled from cod tubulin and bovine MAPs, these microtubules became less sensitive to colchicine. This was not a general effect of MAPs, since bovine MAPs did not induce a colchicine stability of microtubules assembled from bovine tubulin. We can therefore conclude that MAPs can induce colchicine stability of colchicine labile acetylated tubulin.     

Fragments Ba and Bb derived from guinea pig factor B of the properdin system: purification, characterization, and biologic activities.

Functionally active guinea pig factor B was purified by a combination of chromatographic steps including Sephadex G-25, QAE A25, QAE A50, CM C50, and Sepharose 4B coupled with purified cobra venom factor. Purified factor B had a m.w. of 106,000 daltons and a single subunit structure. It was heat labile. After cleavage of native B with cobra venom factor coupled to Sepharose 4B in the presence of D, the resulting two fragments, the larger one (Bb) and the smaller one (Ba), were further purified. The m.w. of Bb and Ba was determined as 64,000 and 53,000 daltons, respectively, by SDS-PAGE. Neither of the fragments evoked a contraction of guinea pig ileum or histamine release from rat mast cells. Only the smaller fragment Ba (at a concentration of 120 nM) stimulated guinea pig peritoneal polymorphonuclear leukocytes to respond with increased movement. This activity as well as the antigenicity of Ba were heat stable, but were sensitive to trypsin digestion, whereas the antigenicity of Bb was heat labile.     

Metabolic activation of N-acetylbenzidine and N,N'-diacetylbenzidine to mutagens, using isolated hepatocytes and the 9000 X g liver supernatant from rat, hamster and guinea pig

The metabolic activation of MABZ and DABZ, forming products mutagenic towards Salmonella typhimurium TA1538, was studied with isolated hepatocytes from rat, hamster and guinea pig and the S9 fraction (9000 X g supernatant) prepared from these hepatocytes. Special attention was given to the influence of acetyl-CoA, the cofactor for N-acetylation, on the mutagenicity of these arylamides. The rat and guinea pig S9 preparation activated MABZ as well as DABZ to a much higher degree than the intact hepatocytes of these animal species. Addition of acetyl-CoA to the S9 preparation decreased the mutagenicity of MABZ and DABZ. On the contrary, for the hamster the mutagenicity of MABZ and DABZ appeared to be lower with the S9 preparation than with intact hepatocytes. Addition of acetyl-CoA to the S9 here increased the mutagenic activity of these arylamides. In the presence of intact hepatocytes obvious interspecies differences were observed in the activation of MABZ and DABZ. DABZ was far more effectively activated by hamster hepatocytes than by rat hepatocytes. This was not found with MABZ. Both substrates were poorly activated by guinea pig hepatocytes.     

Moderate Hypoxia Followed by Reoxygenation Results in Blood-Brain Barrier Breakdown via Oxidative Stress-Dependent Tight-Junction Protein Disruption

Re-canalization of cerebral vessels in ischemic stroke is pivotal to rescue dysfunctional brain areas that are exposed to moderate hypoxia within the penumbra from irreversible cell death. Goal of the present study was to evaluate the effect of moderate hypoxia followed by reoxygenation (MHR) on the evolution of reactive oxygen species (ROS) and blood-brain barrier (BBB) integrity in brain endothelial cells (BEC). BBB integrity was assessed in BEC in vitro and in microvessels of the guinea pig whole brain in situ preparation. Probes were exposed to MHR (2 hours 67-70 mmHg O₂, 3 hours reoxygenation, BEC) or towards occlusion of the arteria cerebri media (MCAO) with or without subsequent reperfusion in the whole brain preparation. In vitro BBB integrity was evaluated using trans-endothelial electrical resistance (TEER) and transwell permeability assays. ROS in BEC were evaluated using 2′,7′-dichlorodihydrofluorescein diacetate (DCF), MitoSox and immunostaining for nitrotyrosine. Tight-junction protein (TJ) integrity in BEC, stainings for nitrotyrosine and FITC-albumin extravasation in the guinea pig brain preparation were assessed by confocal microscopy. Diphenyleneiodonium (DPI) was used to investigate NADPH oxidase dependent ROS evolution and its effect on BBB parameters in BEC. MHR impaired TJ proteins zonula occludens 1 (ZO-1) and claudin 5 (Cl5), decreased TEER, and significantly increased cytosolic ROS in BEC. These events were blocked by the NADPH oxidase inhibitor DPI. MCAO with or without subsequent reoxygenation resulted in extravasation of FITC-albumin and ROS generation in the penumbra region of the guinea pig brain preparation and confirmed BBB damage. BEC integrity may be impaired through ROS in MHR on the level of TJ and the BBB is also functionally impaired in moderate hypoxic conditions followed by reperfusion in a complex guinea pig brain preparation. These findings suggest that the BBB is susceptible towards MHR and that ROS play a key role in this process.     

Species differences in structure-activity relationships of adenosine agonists and xanthine antagonists at brain A1 adenosine receptors

A series of 28 adenosine analogs and 17 xanthines has been assessed as inhibitors of binding of N6-R-[3H]phenylisopropyladenosine binding to A1 adenosine receptors in membranes from rat, calf, and guinea pig brain. Potencies of N6-alkyl- and N6-cycloalkyladenosines are similar in the different species. However, the presence of an aryl or heteroaryl moiety in the N6 substituent results in marked species differences with certain such analogs being about 30-fold more potent at receptors in calf than in guinea pig brain. Potencies at receptors in rat brain are intermediate. Conversely, 2-chloroadenosine and 5'-N-ethylcarboxamidoadenosine are about 10-fold less potent at receptors in calf brain than in guinea pig brain. Potencies of xanthines, such as theophylline, caffeine and 1,3-dipropylxanthine are similar in the different species. However, the presence of an 8-phenyl or 8-cycloalkyl substituent results in marked species differences. For example, a xanthine amine conjugate of 1,3-dipropyl-8-phenylxanthine is 9-fold more potent at receptors in calf than in rat brain and 110-fold more potent in calf than in guinea pig brain. Such differences indicate that brain A1 adenosine receptors are not identical in recognition sites for either agonists or antagonists in different mammalian species.     

Histamine Turnover in the Brain of Different Mammalian Species: Implications for Neuronal Histamine Half-Life

The turnover of neuronal histamine (HA) in nine brain regions and the spinal cord of the guinea pig and the mouse was estimated and the values obtained were compared with data previously obtained in rats. The size of the neuronal HA pool was determined from the decrease in HA content, as induced by (S)-alpha-fluoro-methylhistidine (alpha-FMH), a suicide inhibitor of histidine decarboxylase. The ratios of neuronal HA to the total differed with the brain region. Pargyline hydrochloride increased the tele-methylhistamine (t-MH) levels linearly up to 2 h after administration in both the guinea pig and the mouse whole brain. Regional differences in the turnover rate of neuronal HA, calculated from the pargyline-induced accumulation of t-MH, as well as in the size of the neuronal HA pool, were more marked in the mouse than in the guinea pig brain. The hypothalamus showed the highest rate in both species. There was a good correlation between the steady-state t-MH levels and the turnover rate in different brain regions. Neither the elevation of the t-MH levels by pargyline nor the reduction of HA by alpha-FMH was observed in the spinal cord, thereby suggesting that the HA present in this region is of mast cell origin. The half-life of neuronal HA in different brain regions was in the range of 13-38 min for the mouse and 24-37 min for the guinea pig, except for HA from the guinea pig hypothalamus, which had an extraordinarily long value of 87 min. These results suggest that there are species differences in the function of the brain histaminergic system.     

Tissue distribution of cholesterol feedback control in the guinea pig.

The level of cholesterol synthesis and the activity of the cholesterol feedback system were studied in tissue slices from a number of organs of the guinea pig. In contrast to the tissue distribution of sterol synthesis in the rat, liver slices of the guinea pig have a low rate of sterologenesis, with ileum and lung being the most active sterologenic tissues. More surprising, all tissues studied in the guinea pig, including lung, ileum, and brain, were shown to possess an active cholesterol feedback system. The basis for the widespread organ distribution of cholesterol feedback control in the guinea pig is probably the ability of the various tissues of the guinea pig to take up and concentrate exogenous cholesterol and is not the result of any inherent differences in the lipoprotein composition in this species.     

Tubulin increases with lactation in rat and guinea pig mammary alveolar cells

Summary Changes in mammary gland tubulin were studied immunocytochemically during transition from late pregnancy to lactation. Indirect immunofluorescence was used to localize tubulin in mammary glands from late pregnant, early lactating and peak lactating guinea pigs. Whole rabbit antiserum against guinea pig brain tubulin and affinity-purified antibody indicated increases in alveolar cell tubulin content from late pregnancy through peak lactation coincident with the development of lactation. Only alveolar cells displayed high, specific fluorescence or underwent a developmental increase. Tubulin was concentrated apically, in association with secretory structures. In a second study comparing mammary tissues from 18 days pregnant and 10 days lactating rats, EM immunogold was used with three commercial antitubulins ranging from a rabbit polyclonal antiserum against chick brain MTs to a monoclonal mouse anti-alpha tubulin. Gold particle counts indicated 2- to 5- fold tubulin increases in alveolar cells with lactation and development of an apicobasal (high apical) tubulin gradient. Variations among the three anti-tubulins is discussed. The results confirmed previous observations of whole gland tubulin increases based on colchicine binding assays and localized the site of the increase primarily in alveolar cells.Abbreviations EM electron microscope-(ic) - GAM goat anti-mouse - GAR goat anti-rabbit - Ig immunoglobulin - MC monoclonal - MT microtubule - PAGE polyacrylamide gel electrophoresis - PIPES 1,4-piperazine diethane sulfonic acid - PBS phosphate buffered saline - PC polyclonal - Rb rabbit - SDS sodium dodecyl sulfate Dedicated to Professor Stuart Patton on the occasion of his 70th birthday.