Differential transport properties of two mdr gene products are distinguished by progesterone

P-glycoprotein is an integral membrane protein that is overproduced in multidrug-resistant cells. It is likely to function as an energy-dependent drug efflux pump to maintain intracellular drug concentrations below cytotoxic levels. Individually isolated multidrug-resistant murine cell lines, J7.V1-1 and J7.V3-1, overproduce P-glycoproteins encoded by the mdr1b and mdr1a genes, respectively. The transport properties of these cell lines and the drug binding characteristics of their P-glycoproteins have been compared. It is concluded that 1) the mdr1a gene product is a more efficient efflux pump than the mdr1b gene product, and 2) whereas a single class of vinblastine binding sites is present in J7.V1-1 membrane vesicles, there appears to be two classes of such sites in J7.V3-1 membrane vesicles. The effects of verapamil and progesterone, two compounds that are known to interact with P-glycoprotein, have been analyzed in the two cell lines. Progesterone inhibited drug binding and efflux and increased drug sensitivity to vinblastine with more potency in J7.V1-1 cells than in J7.V3-1 cells. It is concluded that progesterone, but not verapamil, can be used to differentiate the two mdr gene products in the mouse.

Functional expression of murine multidrug resistance in Xenopus laevis oocytes

The development of multidrug resistance (MDR) is associated with the overproduction of a plasma membrane glycoprotein, P glycoprotein. Here we report the functional expression of a member of the murine mdr family of proteins and show that Xenopus oocytes injected with RNA encoding the mouse mdr1b P glycoprotein develop a MDR-like phenotype. Immunological analysis indicated that oocytes injected with the mdr1b RNA synthesized a protein with the size and immunological characteristics of the mouse mdr1b P glycoprotein. These oocytes exhibited a decreased accumulation of [3H]vinblastine and showed an increased capacity to extrude the drug compared to control oocytes not expressing the P glycoprotein. In addition, competition experiments indicated that verapamil, vincristine, daunomycin, and quinidine, but not colchicine, can overcome the rapid drug efflux conferred by the expression of the mouse P glycoprotein.

Suntan, sunburn, and pigmentation factors and the frequency of acquired melanocytic nevi in children. Similarities to melanoma: the Vancouver Mole Study

The association between prevalence of benign melanocytic nevi and a number of skin cancer risk factors was examined among 913 white Vancouver (Canada) school children aged 6 to 18 years. Subjects with light skin, with a propensity to burn rather than tan in the sun, and with numerous or severe sunburns in the previous 5 years had significantly higher nevus counts than individuals without these characteristics. Subjects who acquired deeper tans tended to have fewer nevi than those who did not tan. Finally, children who freckled had higher nevus counts than those who did not freckle. These findings in children are similar to those seen in studies of malignant melanoma among adults and suggest that strategies to reduce melanoma incidence should begin with young children.

Post-hepatitic aplastic anaemia in children in Taiwan, a hepatitis prevalent area

Aplastic anaemia is a rare but serious complication of hepatitis, and hepatitis is an unusual cause of aplastic anaemia in children in the West. However, the relative frequencies of acquired aplastic anaemia in children in Taiwan, a hepatitis prevalent area, differ from those in the West, in the very high frequency of post-hepatitic aplastic anaemia (23.9% of all cases of aplastic anaemia). This may account for the higher incidence of aplastic anaemia in children in Taiwan. Although the prognosis of post-hepatitic severe aplastic anaemia was very poor, the present study using bone marrow transplantation, antithymocyte (or antilymphocyte) globulin, high-dose methylprednisolone and cyclosporin, etc., has improved the response rate and the survival.

Anatomic distribution of acquired melanocytic nevi in white children. A comparison with melanoma: the Vancouver Mole Study

The presence of acquired benign nevi is a risk factor for cutaneous melanoma, yet relatively little is known about the etiology of nevi. We have conducted a study of the prevalence of melanocytic nevi among 1146 white Vancouver (Canada) schoolchildren aged 6 to 18 years. Numbers of nevi per square meter of body surface area increase with age in children of both sexes. Male adolescents have more nevi than female adolescents on the head and neck as well as on the trunk, while prevalence in females is higher on the upper and lower limbs. This distribution parallels that of cutaneous melanoma in British Columbia adults. Nevi are more common in children on intermittently exposed body sites than on constantly or minimally sun-exposed sites. This suggests that exposure to strong intermittent sunlight in childhood (a risk factor for cutaneous melanoma) may also be important in the etiology of acquired benign nevi.

Photoaffinity probes for the alpha 1-adrenergic receptor and the calcium channel bind to a common domain in P-glycoprotein

P-glycoprotein is a 130-180-kDa integral membrane protein that is overproduced in multidrug-resistant cells. The protein appears to act as an energy-dependent drug efflux pump that has broad specificity for structurally diverse hydrophobic antitumor drugs. Many agents, such as the calcium channel blocker verapamil, reverse multidrug resistance and also interact with P-glycoprotein. The goal of this work was to determine if a common binding site participates in the transport of antitumor drugs and/or the reversal of drug resistance. This was done by comparing the peptide maps of P-glycoprotein (encoded by mdr1b) after it was labeled with a photoactive calcium channel blocker, [3H]azidopine, and a newly identified photoaffinity analog for P-glycoprotein 2-[4-(4-azido-3-[125I]iodobenzoyl) piperazin-1-yl]-4-amino-6,7-dimethoxyquinazoline [( 125I]iodoaryl azidoprazosin). [125I] Iodoaryl azidoprazosin, which classically has been used to identify the alpha 1-adrenergic receptor, bound to P-glycoprotein and was preferentially competed by vinblastine greater than actinomycin D greater than doxorubicin greater than colchicine. Peptide maps derived from P-glycoprotein labeled with [3H]azidopine or [125I]iodoaryl azidoprazosin were identical. After maximal digestion under conditions for Cleveland mapping, a single major 6-kDa fragment was obtained after digestion with V8 protease, whereas two major fragments, 6.5 and 5.5 kDa, were detected after digestion with chymotrypsin. The 6.0-kDa V8 fragment and the 6.5-kDa chymotrypsin fragment were both found when P-glycoprotein encoded by mdr1a and mdr1b was compared. Despite its specific interaction with P-glycoprotein, neither iodoaryl azidoprazosin nor prazosin markedly reversed resistance compared with verapamil or azidopine. Further, multidrug-resistant cells were 900-fold resistant to vinblastine but only 5-fold resistant to prazosin. These data demonstrate that structurally diverse reversal and/or antitumor agents are likely to have differential affinity for a small common domain of P-glycoprotein.

The products of the mdr1a and mdr1b genes from multidrug resistant murine cells have similar degradation rates

Two vinblastine-resistant sublines of the murine macrophage-like cell line J774.2, J7.V1-1 and J7.V3-1, overproduce unique forms of P-glycoprotein that are encoded by distinct mdr genes, mdr1b and mdr1a, respectively. Degradation rates of the two P-glycoprotein isoforms were measured by immunoprecipitation of P-glycoprotein. The half-life of immunoprecipitable P-glycoprotein from J7.V1-1 cells was 16.8 +/- 0.5 hours and from J7.V3-1 cells, 17.4 +/- 0.5 hours. This rate was not influenced by the presence of vinblastine in the growth medium. The data indicate that P-glycoproteins derived from distinct genes have similar degradation rates.

Differences in incidence rates of cancers of the respiratory tract by anatomic subsite and histologic type: an etiologic implication

Data from nine population-based cancer registries participating in the Surveillance, Epidemiology, and End Results Program (1973-1982) were analyzed to determine whether the incidence of different histologic types of respiratory tract cancers varies by anatomic location. The variation in cancer incidence among respiratory tract subsites was remarkable for squamous cell carcinoma, but the variation was less prominent for adenocarcinoma. The rates of squamous cell carcinoma and adenocarcinoma along the airways correspond closely with the deposition pattern of large and small smoke particles, respectively. Also, the rates of adenocarcinoma parallel the distribution of surface glandular cells of the respiratory tract. Our results support the hypothesis that anatomy and physiology, in conjunction with size of particles in inhaled cigarette smoke, play an important role in the genesis of specific histologic types of respiratory tract cancers.

[A survey on Campylobacter jejuni high infection in a nursery]

An epidemiologic survey on Campylobacter jejuni infection in a nursery was made in April 1987. It was found that there was a spread of C. jejuni high infection. Two cooks affected by enteritis of C. jejuni were considered to be a reservoir of the infection. Stool cultures were positive for C. jejuni in 43 out of 187 children, with a positive rate of 23%. Eight of the 43 had diarrhea and the others were asymptomatic carriers (24.3%). Controls were set up in another nursery with 238 healthy children and 201 non-diarrheal outpatients; C. jejuni was positive for 11.4% and 7.5%, respectively. The difference was quite significant (P less than 0.005). Results of biotyping on the strains isolated from the two cooks and the children in the nursery showed that all were of C. jejuni biotype 1, except two (4.7%) of the strains from the children, which were E. coli. The authors have suggested that transmission of C. jejuni in the nursery may be caused by contaminated food or person-to-person contact.

Is chronic sunlight exposure important in accounting for increases in melanoma incidence?

Most attempts to relate changes in patterns of sunlight exposure to the rise in incidence of malignant melanoma have concentrated on the positive association between intermittent exposure to sunlight and risk of melanoma. The Western Canada Melanoma Study, however, also detected a significant inverse association between melanoma and chronic or long-term occupational sun exposure in men, with the lowest risk (OR = 0.5) in those with maximum occupational exposure, suggesting that chronic exposure may be protective. Data obtained from Canadian census figures indicated that since 1951 there has been a substantial reduction in the number of males engaged in outdoor occupations in Canadian society. These observations suggest that part of the increase in the incidence of melanoma in low-sunlight areas may be due to a reduction over the past 40 years of the size of this group of individuals "protected" by their exposure to UV light.

Evaluation of methotrexate containing chemotherapeutic regimens in the treatment of childhood undifferentiated non-Hodgkin's lymphoma and B cell acute lymphoblastic leukemia

From September 1983 to October 1988, 13 undifferentiated non-Hodgkin's lymphomas (NHL) of Burkitt's or non-Burkitt's type and 3 B cell acute lymphoblastic leukemias were treated with various multiagent chemotherapy regimens containing modest to high dose methotrexate (HDMTX) infusions. All were children between the ages 2 years 8 months and 14 years 1 month. The group included 13 boys and 3 girls. The lymphomas were located primarily in the head and neck, 5; abdomen, 7; and lymph nodes, 1. The clinical stages at diagnosis were stage I, 1; stage II, 6; stage III, 3; and stage IV, 3. The MTX infusion dosage ranged from 300 to 4,285 mg/M2, and the total cumulative dose per patient ranged from 750 to 30,168 mg/M2. Citrovorum Factor Rescue was given following all MTX infusions, except for 62 of the 300 mg/M2 infusions. The serum MTX levels were monitored following all HDMTX. The chemotherapy related toxicities were graded and analysed. The clinical characteristics, which might predispose to HDMTX-related toxicities, were identified and are discussed. Our data reveals the inpatient and interpatient variations in the kinetics of MTX. There were no drug-related deaths, and the overall outcome of the patients was satisfactory. We conclude that MTX infusion continues to play an important role in the current management of childhood B cell malignancies; however, obstacles still remain, especially for those with widespread B cell disease.

Progesterone interacts with P-glycoprotein in multidrug-resistant cells and in the endometrium of gravid uterus

P-Glycoprotein (P-GP) plays a pivotal role in maintaining the multidrug-resistant (MDR) phenotype. This membrane glycoprotein is overproduced in MDR cells and the endometrium of the mouse gravid uterus (Arceci, R.J., Croop, J.M., Horwitz, S.B., and Housman, D. (1988) Proc. Natl. Acad. Sci. U.S.A. 85, 4350-4354). This latter observation and an interest in endogenous substrates for P-GP led to a study of the interaction of steroids with P-GP found in the endometrium of the mouse gravid uterus and in MDR cells derived from the murine macrophage-like cell J774.2. [3H]Azidopine labeling of P-GP from these two sources was inhibited by various steroids, particularly progesterone. Progesterone also markedly inhibited [3H]vinblastine binding to membrane vesicles prepared from MDR cells, enhanced vinblastine accumulation in MDR cells, and increased the sensitivity of MDR cells to vinblastine. In addition, we have demonstrated that the hydrophobicity of a steroid is important in determining its effect on inhibition of drug binding to P-GP. It is concluded that progesterone, a relatively nontoxic endogenous steroid, interacts with P-GP and is capable of reversing drug resistance in MDR cells.

New phases of DPPC/water mixtures

Hydration of DPPC at low temperatures yielded two new phases, a non-lamellar C1 phase and a lamellar C2 phase, as well as the normal gel phase, depending upon the initial physical state of the dry lipid. From the results of wide-angle diffraction and calorimetry the C2 phase appears very similar to the normal C phase, but the D spacing is considerably larger, suggesting that the C2 phase is a C phase with untilted chains.

Diazepam facilitates reflex bradycardia in conscious rats

The effects of diazepam on cardiovascular function were assessed in conscious rats. Intravenous administration of diazepam (1-30 mg kg-1) produced a dose-dependent decrease in both the mean arterial pressure and the heart rate. Also, reflex bradycardia was produced in rats by intravenous infusion of adrenaline (1.25-2.5 micrograms kg-1). Intravenous pretreatment of the rats with diazepam, although causing no change in the adrenaline-induced pressor effect, did enhance the adrenaline-induced reflex bradycardia. However, the diazepam enhancement of adrenaline-induced reflex bradycardia was antagonized by pretreatment of rats with an intravenous dose of picrotoxin (an agent blocks chloride channels by binding to sites associated with the benzodiazepine-GABA-chloride channel macromolecular complex). The data indicate that diazepam acts through the benzodiazepine-GABA-chloride channel macromolecular complex within the central nervous system to facilitate reflex bradycardia mediated through baroreceptor reflexes in response to an acute increase in arterial pressure.

Kinetics of the subtransition in dipalmitoylphosphatidylcholine

The kinetics of the interconversions of the subgel and gel phases in dipalmitoylphosphatidylcholine have been studied by using differential dilatometry, differential scanning calorimetry (DSC), and neutral buoyancy centrifugation as a function of incubation temperature and deuteriation of the solvent. As seen by others, DSC scans show two peaks in the subgel transition region for incubation temperatures below 1 degree C. After incubation at 0.1 degree C, the DSC peak that occurs at the lower scanning temperature appears with an incubation half-time of 0.5 day and eventually converts into a peak at higher scanning temperature with an incubation half-time of 18 days. By varying the scanning rate, we show that these two peaks merge into one at slow scanning rates with a common equilibrium transition temperature of 13.8 degrees C, in agreement with equilibrium calorimetry and dilatometry (delta V = 0.017 +/- 0.001 mL/g). For incubation temperatures above 4.6 degrees C, only one peak appears in both scanning dilatometry and calorimetry. While the initial rate of subgel conversion is smaller at the higher incubation temperatures, after 300 h a higher percentage of the sample has converted to subgel than at the lower incubation temperatures. We suggest that higher incubation temperatures (near 5 degrees C) are preferable for forming the stable subgel phase, and we present a colliding domain picture that indicates why this may be so. Our results in D2O and the similarity of the kinetics of volume decrease with the kinetics of wide-angle diffraction lines also support the suggestion that the partial loss of interlamellar water plays a kinetic role in subgel formation.

Does prior infertility increase the risk of tubal pregnancy?

One hundred forty-nine patients who underwent surgery for tubal pregnancy at five hospitals in Seattle (WA) between 1975 and 1979 were interviewed to determine the risk factors for this disorder. Their responses were compared with those of 706 control women who had conceived an intrauterine pregnancy during the same time period during which the tubal pregnancies occurred. A higher proportion of cases reported a history of infertility (attempt to conceive without success for a period of at least 1 year) than controls (relative risk [RR] = 2.5; 95% confidence interval [CI] = 1.7-3.7). Women who were diagnosed in the investigation of their infertility as having tubal or ovulatory dysfunction had relative risks of tubal pregnancy of 5.8 (95% CI = 2.1-16.4) and 3.4 (95% CI = 1.3-8.5), respectively. The average time over which subjects had attempted to conceive before index pregnancies that were planned was longer among cases (15.4 months) than among controls (6.9 months). These results support the hypothesis that a history of infertility predisposes women to an increased risk of tubal pregnancy. The authors also found that, among infertile women, about twice as many cases (14.3%) as controls (6.8%) were current fertility drug users (RR = 3.1; 95% CI = 1.1-9.1), which suggests that the use of fertility drug(s) may further increase the risk of tubal pregnancy.

Incidence of histologic types of cancer of the small intestine

Data from nine population-based cancer registries participating in the Surveillance, Epidemiology, and End Results Program from 1973 through 1982 were analyzed to determine the demographic correlates of the incidence of the four major histologic types of cancer of the small intestine: carcinomas, malignant carcinoid tumors, lymphomas, and sarcomas. These tumors were uncommon: The average annual incidence per million persons was 3.9, 2.9, 1.6, and 1.2, respectively. The age-specific incidence rate for each type was quite low through middle age, after which it rose sharply. Males experienced higher rates than females for each of the four histologic types. Blacks were at a 40-70% greater risk than whites for the occurrence of carcinomas and carcinoid tumors but at a 50% lower risk for lymphomas. The reported incidence of malignant carcinoid tumors increased during the decade under study, the rate at the end of the interval being 50% greater than that at the beginning. The extent to which this increase represents improved detection of these tumors or a change in the criteria separating malignant from benign tumors could not be evaluated. There was no change in the incidence of carcinomas, lymphomas, or sarcomas of the small intestine. The four histologic types varied considerably with regard to their proportional distribution among the subsites of the small intestine. Carcinoid tumors, lymphomas, and sarcomas rarely occurred in the duodenum, whereas nearly half of the carcinomas were found there. Eighty-seven percent of the carcinoid tumors and 60% of the lymphomas occurred in the ileum. Clues to the etiologies of tumors of the small intestine are sparse. The incidence data presented here suggest that at least some of the etiologies will differ among the histologic types.

Lymphoblastic lymphoma presenting as a huge intracavitary cardiac tumor causing heart failure

A huge intracavitary cardiac tumor causing heart failure in a 13-year-old girl was detected by two-dimensional echocardiography and was successfully resected to relieve her life-threatening symptoms. On pathologic examination, the tumor was found to be a nonconvoluted lymphoblastic lymphoma of B-cell lineage rather than a myxoma. This case is reported because of its rarity and unusual mode of growth and presentation, and illustrates that lymphoma should be included in the differential diagnosis of pedunculated cardiac tumors, especially in young individuals. The precise cytologic diagnosis of non-Hodgkin's lymphoma is important because chemotherapy and radiotherapy may achieve palliation or control of the disease.

Dilatometric studies of isobranched phosphatidylcholines

Absolute apparent specific volumes have been obtained for phosphatidylcholine lipids with saturated, isobranched hydrocarbon chains with ni = 15 to 20 carbons, with an emphasis upon phase transition behavior, both equilibrium and kinetic. The temperature of the chain-melting transition extrapolates with increasing chain length to the melting temperature of polyethylene with a small odd/even alternation. There are also odd/even alternations in the volume of transition and in the hysteresis of the chain-melting transition, but with the odd and even reversed when compared with the larger odd/even alternation in the lower solid-solid transition that occurs in the longer chain ni lipids. A phenomenological picture is given for the coalescence of the two transitions for shorter ni lipids and this picture is used to sharpen the discussion of the kinetic mechanism of melting. A temperature-reversal experiment shows that the melting from the lowest temperature crystal or C phase to the fluid F phase does not proceed via the metastable gel G phase for 16i. The dilatometric results are combined with recent X-ray structural results for the C and G phases of 17i and 20i to deduce various structural information, including the hydration numbers and the volume of the headgroup, VH = 341 A3, which agrees very well with VH for straight-chain phosphatidylcholines. For the chain-melted F phase the assumption that the methylene volumes of the different ni lipids should be the same at the same temperature is used to obtain the volumes of the methylene and the methyl groups.

Insulin-stimulated sodium transport in toad urinary bladder

Mammalian and teleost insulins increase active sodium transport by the toad urinary bladder at subnanomolar concentrations. This stimulation is evident within 15 min and persists for hours. Porcine proinsulin and a cross-linked derivative of bovine insulin are less effective than porcine insulin in stimulating the short-circuit current (SCC), indicating the specificity appropriate for activation of sodium transport through an insulin receptor. The initial stimulation by insulin of the SCC is not blocked by pretreatment with actinomycin D, puromycin, cycloheximide, or tunicamycin. However, in the presence of any one of these inhibitors the sustained increase in SCC is blocked and the rise is short-lived, lasting only 45 to 90 min. In amphotericin-treated bladders, the addition of insulin did not further stimulate SCC.

Molecular basis for the anti-sickling activity of aromatic amino acids and related compounds: a proton nuclear magnetic resonance investigation

High-resolution proton nuclear magnetic resonance spectroscopy and relaxation techniques have been used to investigate the interactions of sickle cell hemoglobin (Hb S) and human normal adult hemoglobin (Hb A) with p-bromobenzyl alcohol, L-phenylalanine, L-tryptophan, and L-valine. With the exception of valine, all these compounds inhibit the polymerization of deoxy-Hb S [Noguchi, C. T., & Schechter, A. N. (1978) Biochemistry 17, 5455)). Using transferred nuclear Overhauser effects among the proton resonances of the compound of interest and the corresponding longitudinal relaxation rates (T1(-1], we have shown that the binding of each of the compounds investigated to deoxy-Hb S is comparable to that to deoxy-Hb A. Intermolecular transferred nuclear Overhauser effects have been observed between proton resonances of the anti-sickling compounds and specific protons situated in the heme pockets of Hb. On the basis of these results, we suggest that one binding site, common to all compounds with anti-sickling activity, is at or near the heme pockets in the alpha and beta chains of both deoxy-HB S and deoxy-Hb A. The proton T1(-1) values of the histidyl residues situated over the surface of the hemoglobin molecule indicate that a second binding site is located at or near the beta 6 position, containing the mutation in Hb S (beta 6Glu----Val). The binding of the compounds investigated to the latter site induces conformational changes in the amino-terminal domains of the beta chains.(ABSTRACT TRUNCATED AT 250 WORDS)

Thermodynamic studies of purple membrane

Differential dilatometric and differential scanning calorimetric measurements have been made of purple membrane with an emphasis upon the temperature range 5 degrees C less than T less than 45 degrees C. The coefficient of thermal expansion alpha is about 7 X 10(-4)/Cdeg up to 30 degrees C and decreases at higher temperatures. The specific heat increases rapidly with temperature with absolute values in the range 0.30-0.45 cal/Cdeg per g. A nearly constant alpha juxtaposed with a rapidly increasing specific heat is similar to the properties of lipid bilayers in the gel phase and alkanes in the solid phase. This behavior is explained by the concept of hindered vibrations which would now appear to apply to at least one integral membrane protein. There may also be a small broad transition centered near 20-25 degrees C that would correspond to the melting of less than 25 degrees of freedom per bacteriorhodopsin molecule and associated lipids. Using our measured apparent specific volume the average thickness of purple membrane is calculated to be 43.5 A. The specific volume of interaction of lipids and proteins is estimated, using the amino acid sequence of bacteriorhodopsin and average amino acid volumes from structural studies of other proteins, to be about 11% of the specific volume of the purple membrane lipids or 4% of the volume of the bacteriorhodopsin protein. A positive volume of interaction is consistent with lipid-protein interactions being an important determinant of the thermodynamic properties of purple membrane.

A comparison of protein synthetic patterns of MDCK cells grown in serum and hormonally defined serum-free medium

The development of hormonally defined serum-free media (HDM) for the culture of mammalian cells has allowed the study of specific cellular functions in a totally defined environment. Recently, several reports have indicated that there are differences in the basic cellular physiology of cells cultured in HDM when compared to cells cultured by the more traditional method of using serum-supplemented culture media (SM). We report here that there are significant changes in the protein synthetic pattern in MDCK cells grown in HDM. There were no changes exhibited during the first passage in HDM, but following 10 passages in HDM there was an increased isotope ratio of 1) plasma membrane proteins with molecular weights of 12,000, 36,000 and 68,000 and 2) endoplasmic reticulum proteins with molecular weights of 12,000 and 37,000. Additionally, the incorporation of methionine and uridine were significantly increased in cells cultured in HDM for 10 passages. At present, we believe that these changes in the protein synthetic patterns are due at least partially to increased protein synthesis as indicated by monosome/polysome ratios. Therefore, though the use of HDM offers a completely defined system for studying cellular function, results obtained using HDM must be interpreted with caution when comparing them to previous studies that have used SM.

Amino acids injected into the cerebroventricular system induce an enhancement of reflex bradycardia in the rat

The effects of administration of taurine, GABA and glycine, into the lateral cerebral ventricle, on cardiovascular function were assessed in urethane-anaesthetized rats. Intraventricular administration of either taurine (10-30 micrograms), GABA (5-20 micrograms) or glycine (5-20 micrograms) caused a dose-dependent decrease in both the heart rate and the mean arterial pressure. For example, both the heart rate and the mean arterial pressure fell almost immediately and reached their minimum levels about 5 min after an injection of 20 micrograms of taurine. The cardiovascular responses recovered about 30 min after the injection of taurine. Also, reflex bradycardia was produced in the rats by intravenous infusion of adrenaline (1-5 micrograms/kg). Intraventricular pretreatment of the rats with either taurine, GABA or glycine, although causing no change in the adrenaline-induced pressor effect, did enhance the adrenaline-induced reflex bradycardia. However, pretreatment of the rats intravenously with the same dose of taurine, GABA or glycine had no effect on the adrenaline-induced bradycardia. These data indicate that these amino acids act through a central mechanism to facilitate reflex bradycardia mediated through baroceptor reflexes in response to an acute increase in arterial pressure.

Mineralocorticoid-induced membrane proteins in MDCK cells

The Madin-Darby canine kidney (MDCK) cell line, which exhibits properties indicative of a distal tubule origin, evidently binds and responds to mineralocorticoid hormones. We investigated the effects of aldosterone and deoxycorticosterone on protein synthesis in MDCK cells grown either in medium supplemented with serum or in a hormonally defined, serum-free medium. Aldosterone induced the synthesis of at least 2 membrane proteins with molecular weights of 35000 and 14000. The MDCK line may prove a useful model system for examining the mechanism of mineralocorticoid-regulated sodium transport and, in particular, the identification and study of hormone-induced proteins in a homogeneous cell population.

Effects of insulin on ribonucleic acid synthesis in toad urinary bladder

We previously found that the sustained rise in active sodium transport by the toad urinary bladder after exposure to insulin is associated with the synthesis of a membrane protein with a molecular weight of 25,000. Studying the effects of insulin on the incorporation of uridine into RNA of epithelial cells of the bladder, we now report that insulin causes a 39% increase in the incorporation of [3H]uridine into poly(A)-containing RNA extracted from granular cells, the predominant epithelial cell type. The increased accumulation of label in RNA, most notably species ranging from 5-10S, could be demonstrated whether cells were pulsed with [3H]uridine or continuously exposed to the label. Using a reticulocyte lysate system, we compared the translation products of RNA from untreated and insulin-treated granular mucosal cells. Exposure to insulin was associated with the expression of a mRNA coding for a protein with molecular weight of approximately 25,000, similar in size to the insulin-induced membrane protein we previously identified in the intact tissue.

Cell-free translation of RNA isolated from aldosterone-treated toad bladder mucosal cells

The stimulation of sodium transport by aldosterone in target tissues requires the synthesis of both mRNA and proteins. Aldosterone-induced mRNA and proteins have been demonstrated in toad urinary bladder and rat kidney. We have isolated total RNA and poly(A)-containing RNA from hormone-treated and untreated toad bladder mucosal cells for translation in a rabbit reticulocyte lysate system. Aldosterone-induced proteins synthesized in this system have physical properties similar to those of aldosterone-induced proteins synthesized in the intact toad bladder.

Cardiac syncope secondary to glossopharyngeal neuralgia--effectively treated with carbamazepine

A 64-year-old male with glossopharyngeal neuralgia, cardiac asystole and grand mal seizures has been relieved of his attacks by intake of 400 mg of Carbamazepine per day over a 4-year period. Simultaneous EEG-EKG recordings before and after drinking water document the diagnosis.

Comparison of toad bladder aldosterone-induced proteins and proteins synthesized in vitro using aldosterone-induced messenger RNA as template

Using double-labeled isotope techniques, it can be shown that aldosterone induces the synthesis of several proteins in the mitochondria-rich (MR) cells of the toad's urinary bladder. Induced proteins have been identified both in the plasma membrane (mol wt = 170,000, 85,000 and 12,000) and the cytosol (mol wt = 36,000, 12,000 and 6,000) fractions of these mucosal cells. We have also shown that aldosterone (Aldo) induces the synthesis of a class of RNA having the properties of messenger RNA (mRNA). mRNA isolated from Aldo-treated mucosal cells was used as template in a cell-free protein-synthesis system prepared from rabbit reticulocytes. Preparations charged with mRNA from Aldo-treated cells synthesized two proteins that were not labeled when mRNA from control tissues was used as template. The electrophoretic mobility of one of these proteins was similar to an Aldo-induced membrane protein (mol wt = 70,000) found in the intact tissue.

Photocontrol of Anthocyanin Synthesis: V. Further Evidence against the Involvement of Photosynthesis in High Irradiance Reaction Anthocyanin Synthesis of Young Seedlings

Streptomycin and chloramphenicol inhibit the development of the photosynthetic apparatus and enhance anthocyanin synthesis in tomato (Lycopersican esculentum, cv. Beefsteak) and red cabbage (Brassica oleracea, cv. Red Acre) seedlings. The two antibiotics do not affect the basic features of light-dependent anthocyanin formation: the relative effectiveness of different irradiance levels and of different spectral regions and the red-far red reversibility of the response are essentially the same in seedlings grown in water or in solution of the two antibiotics. The action of the two antibiotics on anthocyanin synthesis is probably independent of the action of light. The results provide further evidence that the role played by photosynthesis in high irradiance reaction anthocyanin synthesis of young seedlings is only a minor one, if at all.