Rare adult neuronal ceroid lipofuscinosis associated with CLN6 gene mutations: A case report

BACKGROUND

Adult neuronal ceroid lipofuscinosis (ANCL) can be caused by compound heterozygous recessive mutations in CLN6. The main clinical features of the disease are neurodegeneration, progressive motor dysfunction, seizures, cognitive decline, ataxia, vision loss and premature death.

CASE SUMMARY

A 37-year-old female presented to our clinic with a 3-year history of limb weakness and gradually experiencing unstable walking. The patient was diagnosed with CLN6 type ANCL after the identification of mutations in the CLN6 gene. The patient was treated with antiepileptic drugs. The patient is under ongoing follow-up. Unfortunately, the patient’s condition has deteriorated, and she is currently unable to care for herself.

CONCLUSION

There is presently no effective treatment for ANCL. However, early diagnosis and symptomatic treatment are possible.

A rare case of hepatic sinusoidal occlusive syndrome in a premature neonate with trisomy 21

Trisomy 21 (Down Syndrome) may lead to multiple hematological and hepatobiliary manifestations including the development of transient abnormal myelopoiesis. While many cases resolve, transient abnormal myelopoiesis may lead to significant morbidity and mortality in a small percentage of patients. This condition may present a diagnostic challenge for physicians and currently there is only limited data on effective treatments, particularly with low blast percent transient abnormal myelopoiesis. We present a case of a neonate with trisomy 21 and multiple congenital anomalies who consequently developed hepatic failure with evidence of non-cirrhotic portal hypertension likely due to transient abnormal myelopoiesis. This clinical scenario highlights the need for additional evaluation for transient abnormal myelopoiesis associated hepatic disorder and possibly hepatic sinusoidal occlusive syndrome among trisomy 21 neonates particularly with low blast percentage.

Periorbital erythema and swelling as a presenting sign of lupus erythematosus in tertiary referral centers and literature review

Background Cutaneous lupus erythematosus (CLE) includes a broad range of dermatologic manifestations. Periorbital involvement, however, is a relatively rare clinical presentation of CLE. Objectives This clinical study aimed to investigate the characteristics of this unique presentation of CLE in tertiary medical centers. Methods We enrolled patients with periorbital erythema and swelling as the presenting sign of lupus erythematosus, from January 2003 to November 2017, using the data of 553 pathologically proven CLE cases from the registration database of the Chang Gung Memorial Hospitals in Taiwan. Results We enrolled a total of 25 patients. The mean age was 46.7 years and 68% of the patients were female. Most of the patients (84.0%) presented with unilateral involvement, with the left orbit involved in 15 patients (60%); the upper eyelid was the most frequently involved (72%). Mean duration between the onset of clinical manifestations and the diagnosis of CLE was approximately 59 weeks. Nineteen patients had been previously misdiagnosed. All patients had features compatible with CLE on histopathological examination. In contrast, laboratory analysis of the autoimmune profile often revealed negative results, including those for antinuclear antibodies (25%). Notably, anti-SSA/SSB (45.5%) showed the highest positive rate. During follow-up, six patients developed systemic lupus erythematosus (SLE) and two patients developed Sjögren syndrome. Conclusions The diagnosis of CLE presenting as periorbital erythema and swelling is often delayed because of clinical mimicry and the high proportion of negative results on autoantibody tests. Increased clinical suspicion and prompt histopathological examination are crucial for early diagnosis. Moreover, one-fourth of the patients ultimately developed SLE, which highlights the importance of clinical awareness.

Risk of prostate cancer across different racial/ethnic groups in men with diabetes: a retrospective cohort study

AIM

To examine the associations between prostate cancer, diabetes and race/ethnicity.

METHODS

Using administrative data from British Columbia, Canada for the period 1994 to 2012, we identified men aged ≥50 years with and without diabetes. Validated surname algorithms identified men as Chinese, Indian or of other race/ethnicity. Multivariable Cox regression was used to estimate adjusted risks of prostate cancer according to diabetes status and race/ethnicity.

RESULTS

Our cohort of 160 566 men had a mean (sd) age of 64.7 (9.4) years and a median of 9 years' follow-up. The incidence rates of prostate cancer among those with and without diabetes were 177.4 (171.7-183.4) and 216.0 (209.7-222.5) per 1000 person-years, respectively. The incidence among Chinese men was 120.9 (109.2-133.1), among Indian men it was 144.1 (122.8-169.0) and in men of other ethnicity it was 204.8 (200.2-209.5). Diabetes was independently associated with a lower risk of prostate cancer (adjusted hazard ratio 0.82, 95% CI 0.78-0.86), as was Chinese (adjusted hazard ratio 0.54, 95% CI 0.46,0.63) and Indian (adjusted hazard ratio 0.66, 95% CI 0.49,0.89) race/ethnicity; however, there was no statistically significant interaction between diabetes status and race/ethnicity (all P>0.1).

CONCLUSION

Diabetes and Chinese and Indian race/ethnicity were each independently associated with a lower risk of prostate cancer.

Progress in Drug Treatment of Cerebral Edema

Cerebral edema causes intracranial hypertension (ICH) which leads to severe outcome of patients in the clinical setting. Effective anti-edema therapy may significantly decrease the mortality in a variety of neurological conditions. At present drug treatment is a cornerstone in the management of cerebral edema. Osmotherapy has been the mainstay of pharmacologic therapy. Mannitol and hypertonic saline (HS) are the most commonly used osmotic agents. The relative safety and efficacy of HS and mannitol in the treatment of cerebral edema and reduction of enhanced ICP have been demonstrated in the past decades. Apart from its osmotic force, HS exerts anti-edema effects partly through inhibition of Na(+)-K(+)-2Cl(-) Cotransporter-1 (NKCC1) and aquaporin 4 (AQP4) expression in astrocytes. Melatonin may also reduce brain edema and exert neuroprotective effect on several central nervous system diseases through inhibition of inflammatory response. The inhibitors of Na/H exchanger, NKCC and AQP4 may attenuate brain edema formation through inhibition of excessive transportation of ion and water from blood into the cerebral tissue. In this review we survey some of the most recent findings in the drug treatment of brain edema focusing on the use of osmotherapy, melatonin and inhibitors of ion cotransporters and water channels. A better understanding of the molecular mechanism of these agents would help to improve in the clinical management of patients with brain edema.

Epoxyeicosatrienoic acids protect cardiac cells during starvation by modulating an autophagic response

Epoxyeicosatrienoic acids (EETs) are cytochrome P450 epoxygenase metabolites of arachidonic acid involved in regulating pathways promoting cellular protection. We have previously shown that EETs trigger a protective response limiting mitochondrial dysfunction and reducing cellular death. Considering it is unknown how EETs regulate cell death processes, the major focus of the current study was to investigate their role in the autophagic response of HL-1 cells and neonatal cardiomyocytes (NCMs) during starvation. We employed a dual-acting synthetic analog UA-8 (13-(3-propylureido)tridec-8-enoic acid), possessing both EET-mimetic and soluble epoxide hydrolase (sEH) inhibitory properties, or 14,15-EET as model EET molecules. We demonstrated that EETs significantly improved viability and recovery of starved cardiac cells, whereas they lowered cellular stress responses such as caspase-3 and proteasome activities. Furthermore, treatment with EETs resulted in preservation of mitochondrial functional activity in starved cells. The protective effects of EETs were abolished by autophagy-related gene 7 (Atg7) short hairpin RNA (shRNA) or pharmacological inhibition of autophagy. Mechanistic evidence demonstrated that sarcolemmal ATP-sensitive potassium channels (pmK_ATP) and enhanced activation of AMP-activated protein kinase (AMPK) played a crucial role in the EET-mediated effect. Our data suggest that the protective effects of EETs involve regulating the autophagic response, which results in a healthier pool of mitochondria in the starved cardiac cells, thereby representing a novel mechanism of promoting survival of cardiac cells. Thus, we provide new evidence highlighting a central role of the autophagic response in linking EETs with promoting cell survival during deep metabolic stress such as starvation.

PD-1/PDL1 and CD28/CD80 pathways modulate natural killer T cell function to inhibit hepatitis B virus replication

α-Galactosylceramide (α-GalCer)-activated natural killer T (NKT) cells have antiviral properties against hepatitis B virus (HBV). However, α-GalCer activation of NKT cells can induce anergy. We hypothesized that this effect may be overcome by a treatment strategy that includes manipulation of CD28/CD80 costimulatory and PD-1/PDL1 coinhibitory signals of NKT cells, thereby enhancing the anti-HBV effect of α-GalCer. We established a transgenic mouse model of chronic HBV infection and investigated hepatic NKT cell frequencies, functions and expression of immunomodulatory factors. Our results showed that compared with uninfected control mice, hepatic NKT cells from HBV transgenic mice displayed lower frequencies (7.91% vs 16.74%, P < 0.05), impaired capabilities to produce interferon (IFN)-γ (5.6% vs 1.4%, P < 0.05) and interleukin (IL)-4 (6.8% vs 0.3%, P < 0.05), higher expression of PD-1 (9.64% vs 6.36%, P < 0.05) and lower expression of CD28 (5.05% vs 28.88%, P < 0.05). However, when hepatic mononuclear cells (MNCs) were isolated from HBV transgenic mice, α-GalCer exposure in culture remarkably upregulated both PD-1(+) NKT cells (P < 0.05) and CD28(+) NKT cells (P < 0.05). Furthermore, when HBV transgenic mice were treated with combination therapies consisting of α-GalCer and anti-PDL1 monoclonal antibody (mAb) and/or anti-CD80/anti-CD28 mAbs, IFN-γ(+) NKT cell frequency was selectively increased (P < 0.05) and HBV replication was suppressed; these effects were accompanied by varying degrees and types of liver damage. Surprisingly, activating CD28/CD80 signal in HBV transgenic mice was more effective but caused less liver injury than blocking PD-1/PDL1 signal in modulating αGalCer-activated NKT cell function to inhibit HBV infection. Our findings also show that combined therapy with blocking PD-1/PDL1 and activating CD28/CD80 signal in the presence of aGalCer cannot superimpose the effect of antivirus. α-GalCer combination therapy that modulates the CD28/CD80 pathways of NKT cells may represent a promising approach to inhibit HBV replication in chronically infected patients.

Hypertonic saline ameliorates cerebral edema through downregulation of aquaporin-4 expression in the astrocytes

Osmotherapy with 10% hypertonic saline (HS) alleviates cerebral edema through osmotic force. Aquaporin-4 (AQP4) has been reported to be implicated in the pathogenesis of cerebral edema resulting from a variety of brain injury. This study aimed to determine if 10% hypertonic saline ameliorates cerebral edema through downregulation of AQP4 expression in the perivascular astrocytes in the ischemic cerebral edema. Adult male Sprague-Dawley (SD) rats were subjected to permanent right-sided middle cerebral artery occlusion (MCAO) and treated with a continuous i.v. infusion of 10% HS. Brain water content (BWC) analyzed by wet-to-dry ratios in the ischemic hemisphere of SD rats was attenuated after 10% HS treatment. This was coupled with the reduction of neuronal apoptosis in the peri-ischemic brain tissue. Concomitantly, downregulated expression of AQP4 in the perivascular astrocytes after 10% HS treatment was observed. Our results suggest that in addition to its osmotic force, 10% HS exerts anti-edema effects possibly through downregulation of AQP4 expression in the perivascular astrocytes. The reduction of brain edema after 10% HS administration can prevent ischemic brain damage.

A comparison on the emission of polycyclic aromatic hydrocarbons and their corresponding carcinogenic potencies from a vehicle engine using leaded and lead-free gasoline

Our objective in this study was to assess the effect of using two kinds of lead-free gasoline [including 92-lead-free gasoline (92-LFG) and 95-lead-free gasoline (95-LFG), rated according to their octane levels] to replace the use of premium leaded gasoline (PLG) on the emissions of polycyclic aromatic hydrocarbons (PAHs) and their corresponding benzo[a]pyrene equivalent (BaP(eq)) amounts from the gasoline-powered engine. The results show that the three gasoline fuels originally contained similar total PAHs and total BaP(eq) contents; however, we found significant differences in the engine exhausts in both contents. The above results suggest that PAHs originally contained in the gasoline fuel did not affect the PAH emissions in the engine exhausts. The emission factors of both total PAHs and total BaP(eq) obtained from the three gasoline fuels shared the same trend: 95-LFG > PLG > 92-LFG. The above result suggests that when PLG was replaced by 95-LFG, the emissions would increase in both total PAHs and total BaP(eq), but when replaced by 92-LFG would lead to the decreased emissions of both contents. By taking emission factors and their corresponding annual gasoline consumption rates into account, we found that both total PAH and total BaP(eq) emissions increased from 1994 to 1999. However, the annual increasing rates in total BaP(eq) emissions were slightly higher than the corresponding increasing rates in total PAHs.

Effects of methanol-containing additive on emission characteristics from a heavy-duty diesel engine

This study was aimed to investigate the effect of methanol-containing additive (MCA) on the regulated emissions of hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NOx), particulate matter (PM), as well as the unregulated carbon dioxide (CO2) and polycyclic aromatic hydrocarbons (PAHs) from a diesel engine. The engine was tested on a series of diesel fuels blended with five additive levels (0, 5, 8, 10 and 15% of MCA by volume). Emissions tests were performed under both cold- and hot-start transient heavy-duty federal test procedure (HD-FTP) cycles and two selected steady-state modes. Results show that MCA addition slightly decreases PM emissions but generally increases both THC and CO emissions. Decrease in NOx emissions was found common in all MCA blends. As for unregulated emissions, CO2 emissions did not change significantly for all MCA blends, while vapor-phase and particle-associated PAHs emissions in high load and transient cycle tests were relatively low compared to the base diesel when either 5 or 8% MCA was used. This may be attributed to the lower PAHs levels in MCA blends. Finally, the particle-associated PAHs emissions also showed trends quite similar to that of the PM emissions in this study.

Artificial nucleases

The oxidation of DNA and RNA provides a facile approach for investigating the interaction of nucleic acids with proteins and oligonucleotides. In this article, we have outlined our understanding of the mechanism of DNA scission by 1,10-phenanthroline-copper(I) in the presence of hydrogen peroxide. We also discuss results obtained by using 1,10-phenanthroline-oligonucleotide conjugates in probing the size of the transcriptionally active open complex. Finally, we outline an effective method for converting DNA-binding proteins into site-specific modification agents by using 1,10-phenanthroline-copper(I).

Stoichiometry of complexes between mannose-binding protein and its associated serine proteases. Defining functional units for complement activation

Serum mannose-binding protein (MBP) initiates the lectin branch of the complement cascade by binding to sugars on the surfaces of microorganisms and activating two MBP-associated serine proteases (MASP-1 and MASP-2). Rat serum MBP consists of oligomers containing up to four copies of a subunit that is composed of three identical polypeptide chains. Biophysical analysis of intact and truncated MASPs indicates that each MASP is a homodimer that is stabilized through interactions involving an N-terminal CUB domain. The binding sites for MBP are formed from the three N-terminal MASP domains, in which two CUB modules interact with MBP. Each MASP dimer contains binding sites for two MBP subunits. Both sites must be occupied by subunits from a single MBP oligomer to form a stable complex. Thus, the smallest functional unit for complement activation consists of MBP dimers bound to MASP-1 or MASP-2 homodimers. Trimers and tetramers of MBP form complexes containing up to two MASPs. The results reveal how MASP-1 and MASP-2 can function independently to activate the complement cascade.

Effect of fuel aromatic content on PAH emission from a heavy-duty diesel engine

Polycyclic aromatic hydrocarbons (PAHs) emission tests for a heavy-duty diesel engine fueled with blend base diesel fuel by adding batch fractions of poly-aromatic and mono-aromatic hydrocarbons, Fluorene and Toluene, respectively, were simulated to five steady-state modes by a DC-current dynamometer with fully automatic control system. The main objective of this study is to investigate the effect of total aromatic content and poly-aromatic content in diesel fuels on PAH emission from the HDD engine exhaust under these steady-state modes. The results of this study revealed that adding 3% and 5% (fuel vol%) Fluorene in the diesel fuel increases the amount of total-PAH emission by 2.6 and 5.7 times, respectively and increases the amount of Fluorene emission by 52.9 and 152 times, respectively, than no additives. However, there was no significant variation of PAH emission by adding 10% (vol%) of Toluene. To regulate the content of poly-aromatic content in diesel fuel, in contrast to the total aromatic content, will be more suitable for the management of PAH emission.

Effect of methanol-containing additive on the emission of carbonyl compounds from a heavy-duty diesel engine

This study was aimed at determining the effect of methanol-containing additive (MCA) on the emission of carbonyl compounds (CBCs) generated from the diesel engine. For this experiment, a heavy-duty diesel engine was connected with a full flow critical flow ventri (CFV) type dilution tunnel, a Schenck GS-350 DC dynamometer, and a DC-IV control system in series. The operating conditions of the heavy-duty diesel engine for both cold-start and hot-start Transient Cycle tests and for both low-load and high-load steady-state tests were ascertained. The exhaust of CBCs collected from a 2,4-dinitrophenylhydrazine (2,4-DNPH)-coated cartridge were first converted to corresponding hydrazone derivatives, which were then solvent-eluted and analyzed by a High Performance Liquid Chromatograph (HPLC) with an ultraviolet-visible (UV) detector. When either 10% or 15% MCA was used, the emission factors of the CBCs acrolein and isovaleraldehyde increased by at least 91%. Accordingly, future studies must be done to cut down the emission of CBCs when MCA and methanol alternative fuels are used.

Visible-band testbed projector with a replicated diffractive optical element

Raytheon has designed, fabricated, and tested a diffractive-optical-element-based (DOE-based) testbed projector for direct and indirect visual optical applications. By use of a low-cost replicated DOE surface from Rochester Photonics Corporation for color correction the projector optics bettered the modular transfer function of an equivalent commercial camera lens. The testbed demonstrates that a practical DOE-based optical system is suitable for both visual applications (e.g., head-mounted displays) and visual projection (e.g., tactical sensors). The need for and the proper application of DOE's in visual optical systems, the nature and the performance of the projector optical design, and test results are described.

Prevention of acute hyponatremia by mannitol: an unanticipated mechanism

PURPOSE

To evaluate the effectiveness and mode of action of the osmotic diuretic mannitol to prevent the development of acute hyponatremia in a setting designed to mimic the acute hyponatremia observed on the day of surgery.

RESULTS

Hyponatremia (129+/-1 mM, fall of 10+/-1 mM, p <0.01) was induced by the intraperitoneal administration of half-isotonic saline plus DDAVP to rats (n = 8); hyponatremia was due to a positive balance of electrolyte-free water (EFW). Rats given mannitol (10 mmol/kg body wt) in addition to the hypotonic saline plus DDAVP had only a minor degree of hyponatremia (plasma [Na+] 136+/-1 mM, fall 3+/-2 mM, p >0.05). All the mannitol given was excreted over the 16 h of observation, but the urine volume was not higher in these rats. The higher rate of excretion of EFW was due to a marked reduction in the rate excretion of Na+ with mannitol. This antinatriuresis was also present when mannitol was given intravenously.

CONCLUSIONS

Although mannitol increased the excretion of EFW, the mechanism required an enhanced renal reabsorption of Na+ rather than an increase in the urine flow rate.

Physiological disposal of the potential alkali load in diet of the rat: steps to achieve acid-base balance

The purpose of this study was to provide a better understanding of the physiological role of endogenous net organic acid production in rats consuming their usual diet. Balance studies were performed over 24 h, and urine was collected in the day and night portions of the diurnal cycle. A supplemented low-electrolyte diet(LED) was fed to determine whether urinary organic anions were identical to those in the diet. A titration procedure was developed to determine the pK of titratable groups in the urine of rats studied with and without an acid load. Although normal rats excreted net acid (NAE), the latter was inversely related to the amount of food consumed. The rates of excretion of bicarbonate (HCO3), citrate, unmeasured organic anions, and NH+4 were higher in the night portion of the diurnal cycle. NAE rose dramatically when alkali intake was decreased by consuming the LED. Dietary and urinary organic anions were not identical because rats fed the LED supplemented with potassium citrate excreted <10% of this alkali load as citrate and <25% as HCO3. In the 24 h after 3,000 ¿mol NH4Cl was given intraperitoneally, H+ did not appear to be retained, yet NAE rose by only close to 2,000 ¿eq. The rate of excretion of titratable groups with a pK in the 3 to 5 pH range fell by close to 1,000 ¿eq; most of these changes occurred in the first 7 h after NH4Cl was given. We conclude that rat chow provides a large net alkali load. There appear to be two types of endogenous acid production, a form associated with a rise in NAE (e.g., sulfuric acid) and dietary alkali-driven endogenous net acid production, which titrates this alkali. Renal excretion of organic anions makes these acids end products of metabolism.

Hyponatremia in the rat in the absence of positive water balance

The purpose of this report is to determine the mechanisms that lead to hyponatremia when isotonic saline was the only fluid infused into rats given antidiuretic hormone (ADH), and what might minimize the degree of this hyponatremia. Normal rats were deprived of food and water for the 24-hr study period. They received an infusion of isotonic saline to expand their extracellular fluid (ECF) volume with and without exogenous ADH administration (N = 8 in each of the four groups). Similar studies were also carried out in 32 rats fed a low electrolyte diet for 72 hr before the experiment. An additional control group was fed the low electrolyte diet supplemented with sodium (Na), potassium (K), and chloride (Cl). Hyponatremia developed over 24 hr in rats fed their usual diet if treated with ADH and isotonic saline (fall, 13 +/- 2 mM, P < 0.01). The hyponatremia was caused by negative balance for Na + K salts. Hyponatremia did not develop after the saline + ADH treatment if rats were pretreated for 3 days with a low electrolyte diet. Two factors were required to develop this hyponatremia--generation of electrolyte-free water as a result of the excretion of a large quantity of Na + K salts at a high concentration in the urine, and prevention of the excretion of this electrolyte-free water by ADH. Increasing the avidity for Na reabsorption by the kidney prevented this type of hyponatremia from developing.

What is the impact of potassium excretion on the intracellular fluid volume: importance of urine anions

Hyponatremia is a common electrolyte abnormality that causes symptoms as a result of swelling of brain cells. We evaluated the impact of a negative balance for sodium (Na) and potassium (K) salts on the intracellular fluid (ICF) volume, emphasizing the role of anions excreted with K. Rats (N = 10) were deprived of food and water for 24 hours. They received half-isotonic saline to expand their extracellular fluid (ECF) volume by 20%; a long acting antidiuretic hormone (DDAVP) preparation was given to prevent the excretion of electrolyte-free water. The concentration of Na in plasma fell from 139 +/- 1 mM to 120 +/- 2 mM 24 hours after the infusion of hypotonic saline (P < 0.01). Since these rats had a small negative balance for water (4 +/- 1 ml), hyponatremia was due to their negative balances for Na (2.2 +/- 0.3 mmol) and K (2.2 +/- 0.1). There were negative balances for Cl (2.4 +/- 0.2 mmol) and phosphate (0.7 +/- 0.05 mmol). Despite the negative balance for NaCl, the ECF volume as assessed by 3H-inulin space was not contracted. In this model for acute hyponatremia, its basis was electrolyte loss, but the ECF volume was not contracted, suggesting that water shifted from the ICF to the ECF. Hyponatremia is associated with cell swelling only if its cause is positive water balance and/or is loss of Na from the ECF. It is critical to examine the urine anions to determine the compartment of origin of particles excreted with K and thereby whether hyponatremia will result in overall expansion or contraction of the ICF volume.

Alkali therapy extends the period of survival during hypoxia: studies in rats

The goal of this study was to evaluate whether sodium bicarbonate might be a useful form of therapy for hypoxic L-lactic acidosis; our aim was to determine if alkali could extend the time of survival in this setting. Hypoxia was induced in anesthetized, paralyzed, artificially ventilated rats by lowering inspired O2 to 5.5%, an amount sufficient to develop a severe degree of L-lactic acidosis. Measuring arterial blood gases frequently permitted maintenance of a near-constant arterial O2 content. Three groups of hypoxic rats were studied: first, no infusions (n = 10); second, sodium bicarbonate at a rate equal to H+ production in the no-infusion group (n = 12); and third, a control for the Na load in the second group as NaCl (n = 17). Survival was close to twofold longer in the sodium bicarbonate group. Part of this beneficial effect seemed to be increased anaerobic glycolysis, producing ATP along with L-lactic acid. In addition, there was a large decrease in the metabolic demand (consumption of O2) in the 7- to 15-min period in the sodium bicarbonate group. Rats exposed to hypoxia and infused with NaCl for 15 min or alkali for 15, 27, or 40 min were then returned to room air; all survived for the subsequent experimental period of 150 min. We found that there is both a rationale and experimental evidence for giving sodium bicarbonate to prolong survival during hypoxia.

Antikaliuretic action of trimethoprim is minimized by raising urine pH

This study was designed to test the hypothesis that the antikaliuresis caused by trimethoprim could be diminished by alkalinizing the luminal fluid in the CCD, thereby converting trimethoprim from its cationic, active form to an electroneutral, inactive, form. Trimethoprim-induced inhibition of transepithelial Na+ transport was examined in A6 distal nephron cells by analysis of short circuit current. The voltage-dependence of the trimethoprim-induced block of Na+ channels was examined with patch clamp recordings of A6 cells. The antikaliuretic effect of trimethoprim was examined in vivo in rats pretreated with deoxycorticosterone and with NH4Cl to lower urine pH, and in rats also receiving acetazolamide to raise urine pH. We found that the concentration of trimethoprim required to inhibit the amiloride sensitive component of short circuit current by 50% (IC50) was 340 microM (at pH 8.2) and 50 microM (at pH 6.3). The IC50S of protonated trimethoprim were similar (34 microM at pH 8.2 and 45 microM at pH 6.3). The mean time open for the high selectivity, Na+ channel was reduced from 1679 +/- 387 msec to 502 +/- 98 msec with addition of 10-5 M trimethoprim to patch pipette solution at the resting membrane potential (-Vpipette = 0 mV). further decreases in mean time open were observed as -Vpipette was reduced (that is, apical membrane hyperpolarization) to -40 mV (mean time open = 217 +/- 85 msec) and to -80 mV (mean time open = 69 +/- 13 msec). In vivo, trimethoprim caused a > 50% reduction in potassium (K+) excretion due primarily to a fall in the [K+] in the lumen of the terminal CCD. This effect of trimethoprim was markedly attenuated in an alkaline urine induced by acetazolamide. We conclude that it is the charged, protonated species of trimethoprim which blocks epithelial Na+ channels. Increasing urinary pH decreases the concentration of the charged species of trimethoprim and minimizes its antikaliuretic effect.

Footprinting RNA-protein complexes following gel retardation assays: application to the R-17-procoat-RNA and tat--TAR interactions

RNA-protein complexes isolated following a gel retardation assay can be footprinted within the gel matrix using the chemical nuclease activities of 4,7-dimethyl-, 5,6-dimethyl-, and 3,4,7,8-tetramethyl-1,10-phenanthroline-copper. These complexes are more reactive than 1,10-phenanthroline-copper but share its reaction preference for bulges and loops. The interaction of the coat protein of R-17 with its viral RNA target and tat- and tat-derived peptides with HIV TAR RNA have been studied. In both cases, the RNA sequence opposite a 2-3 nucleotide bulge are protected. Tat-derived peptides inhibit cleavage at sites which intact tat does not protect. These results are consistent with transcription studies which have suggested that truncation of tat increases nonspecific binding.

Sequence-specific scission of DNA by the chemical nuclease activity of 1,10-phenanthroline-copper(I) targeted by RNA

RNAs modified with the chemical nuclease 1,10-phenanthroline-copper(I) can achieve the sequence-specific scission of single- and double-stranded DNA targets. The RNAs are prepared in vitro by using 5-(3-aminoallyl)-UTP as the sole source of UTP and can be readily modified with 1,10-phenanthroline by using N-succinimidyl 3-(2-pyridyl-dithio)propionate (SPDP) to cross-link the ligand to the aminoallyl moiety. Single-stranded DNAs are efficiently cleaved at multiple sites because 1,10-phenanthroline is incorporated at several uridines in the sequence. Sequence-specific double-stranded scission of duplex DNA can also be accomplished with 1,10-phenanthroline-derivatized RNA within R loops. These triple-stranded structures form in 70% formamide and involve the displacement of one strand of DNA by the RNA of identical sequence. R loop-directed scission is the first method for DNA scission applicable to any sequence. A unique application of R loop-targeted nucleolytic scission, which relies on its ability to cut DNA at any sequence, is the determination of the distance between two marker DNA sequences within a target. In this case, 1,10-phenanthroline-linked RNAs are prepared from the two distinct sequences and used to cut the DNA fragment after R-loop formation. The size of the fragment liberated by these methods is a direct measure in base pairs of the distance between the two DNA sequences. For example, the distance separating two chicken delta crystallin (delta 1 and delta 2) genes has been confirmed as 24 kilobases by this method.

Fuel selection and the production of ammonium by the kidney: studies using insulin

The purpose of this study was to explore the interrelations among energy turnover, the selection of fuels, and the production of ammonium (NH4+) in the kidney during chronic metabolic acidosis. Experiments were carried out in dogs because of the extensive background literature in this species. The specific question addressed was, will a diminished rate of oxidation of fatty acids in the kidney permit the rate of extraction of glutamine and the production of NH4+ to rise? Chronic metabolic acidosis was induced by the ingestion of NH4Cl for 5 days to stimulate the rate of production of NH4+. Insulin was administered to diminish the delivery of fatty acids to the kidney. The concentration of fatty acids in plasma fell from 350 +/- 104 to 188 +/- 45 microM, yet there was no significant increase in the rates of production of NH4+, consumption of oxygen, or extraction of glutamine after insulin. Notwithstanding, there was a significant rise in the rate of extraction of lactate by the kidney when expressed per 100-mL glomerular filtration rate. Because there was a significant decline in the level of glutamine in plasma (512 +/- 76 to 359 +/- 42 microM) 1 h after giving insulin, a second series of experiments was carried out. When glutamine was infused after the insulin period, there was no longer a fall in the concentration of this metabolite. Notwithstanding, the rates of extraction of glutamine and production of NH4+ were not higher in the presence of insulin. These data suggest that the rate of oxidation of fatty acids did not limit the rate of oxidation of glutamine in the kidneys of fed dogs with chronic metabolic acidosis.(ABSTRACT TRUNCATED AT 250 WORDS)

1,10-Phenanthroline-copper, a footprinting reagent for single-stranded regions of RNAs

The 1,10-phenanthroline-cuprous complex (OP-Cu) with hydrogen peroxide as a coreactant nicks the single-stranded loops and bulges of RNA stem-loop structures more rapidly than the double-stranded stems. This chemical nuclease is therefore a useful footprinting reagent for these regions and can be used to monitor both intramolecular and intermolecular hybridization of single-stranded domains. The formation of A-form structures characteristic of either RNA-RNA or RNA-DNA duplexes inhibits scission because it blocks the binding site of the coordination complex in single-stranded loops and not because the oxidatively sensitive hydrogens of the ribose moiety are blocked. The C-4' and C-1' hydrogens are accessible to solvent in A-structures.

Energy turnover and the production of ammonium by the kidney: effect of hypernatremia

The purpose of this study was to explore further the relation between the rates of oxygen consumption and ammonium (NH4+) production in the kidney during chronic metabolic acidosis. The experimental model was the dog with chronic metabolic acidosis because of the extensive background literature in this species. Chronic metabolic acidosis was produced by the ingestion of 10 mmol NH4Cl/kg body weight for 5 days. There was a significant increase in the rate of oxygen extraction when hypernatremia was present. Despite this rise in the rate of oxygen consumption, there was no increase in the rate of NH4+ production nor in the rate of glutamine extraction. These data suggest that hypernatremia might prevent a further augmentation in glutamine extraction when the rate of oxygen consumption rises. In addition, a larger proportion of the NH4+ produced was excreted in the urine during hypernatremia. This increase was associated with a rise in the urine flow rate, but not with a fall in urine pH.

Is urea formation regulated primarily by acid-base balance in vivo?

Large quantities of ammonium and bicarbonate are produced each day from the metabolism of dietary protein. It has recently been proposed that urea synthesis is regulated by the need to remove this large load of bicarbonate. The purpose of these experiments was to test whether the primary function of ureagenesis in vivo is to remove ammonium or bicarbonate. The first series of rats were given a constant acid load as hydrochloric acid or ammonium chloride; individual rats received a constant nitrogen load at a time when their plasma acid-base status ranged from normal (pH 7.4, 28 mM HCO3) to severe metabolic acidosis (pH 6.9, 6 mM HCO3). Urea plus ammonium excretions and the blood urea, glutamine, and ammonium concentrations were monitored with time. Within the constraints of non-steady-state conditions, the rate of urea synthesis was constant and the plasma glutamine and ammonium concentrations also remained constant; thus it appears that the rate of urea synthesis was not primarily regulated by the acid-base status of the animal in vivo over a wide range of plasma ammonium concentrations. In quantitative terms, the vast bulk of the ammonium load was converted to urea over 80 min; only a small quantity of ammonium appeared as circulating glutamine or urinary ammonium. Urea synthesis was proportional to the nitrogen load. A second series of rats received sodium bicarbonate; urea synthesis was not augmented by a bicarbonate load. We conclude from these studies that the need to dispose of excess bicarbonate does not primarily determine the rate of ureagenesis in vivo. The data support the classical view that ureagenesis is controlled by the quantity of ammonium to be removed.

Substrate utilization by the distal nephron in dogs with chronic metabolic acidosis: studies with ethacrynic acid

Glutamine and lactate oxidations provide the bulk of ATP required for sodium reabsorption in the dog kidney during chronic metabolic acidosis. Indirect evidence has suggested that glutamine is oxidized in the proximal convoluted tubule; if this is true, lactate should be the major fuel of the more distal nephron sites. The purpose of these experiments was to determine which substrates were metabolized by the acidotic dog kidney when a significant proportion of sodium chloride reabsorption was inhibited in the thick ascending limb of the loop of Henle. Ethacrynic acid, a loop diuretic, caused the fractional excretion of sodium to increase from 1 to 34%. The glomerular filtration rate declined somewhat, but there was no significant change in the renal blood flow rate. Renal oxygen consumption declined in conjunction with the natriuresis. However, when the data were examined at a constant filtered load of sodium (a constant rate of ATP turnover), there was no reduction in glutamine uptake or glutamine conversion to ATP in the presence of this natriuretic agent. The major change observed concerned lactate metabolism, in the presence of ethacrynic acid, there was no longer a significant rate of lactate extraction. These data are best explained by assuming that glutamine is the fuel of the proximal convoluted tubule of the acidotic dog kidney, whereas lactate oxidation occurs principally in the nephron sites where sodium reabsorption was inhibited by ethacrynic acid.

Effect of the blood lactate concentration on renal glutamine metabolism in dogs with chronic metabolic acidosis

It appears that glutamine and lactate are the principal substrates for the kidney in dogs with chronic metabolic acidosis. Accordingly, the purpose of this study was to determine if a higher or lower rate of renal lactate extraction would influence the rate of glutamine extraction at a constant rate of renal ATP turnover. The blood lactate concentration was 0.9 +/- 0.01 mM in 15 acidotic dogs. However, eight dogs with chronic metabolic acidosis had a spontaneous blood lactate concentration of 0.5 mM or lower. The kidneys of these dogs extracted considerably less lactate from the arterial blood (19 vs. 62 mumol/100 mL glomerular filtration rate (GFR]. Nevertheless, glutamine, alanine, citrate, and ammonium metabolism were not significantly different in these two groups of dogs. Renal ATP balance in acidotic dogs with a low blood lactate could only be achieved if a substrate other than additional glutamine were oxidized in that segment of the nephron which normally oxidized lactate; presumably a fat-derived substrate and (or) lactate derived from glucose was now the metabolic fuel at these more distal sites. When the blood lactate concentration was greater than 1.9 mM, lactate extraction rose to 219 mumol/100 mL GFR. Glutamine, alanine, citrate, and ammonium metabolism were again unchanged; in this case, ATP balance required substrate flux to products other than carbon dioxide, presumably, gluconeogenesis. It appears that renal ammoniagenesis is a proximal event and is independent of the rate of renal lactate extraction.

Template-directed synthesis on oligodeoxycytidylate and polydeoxycytidylate templates

Oligodeoxycytidylic acids and polydeoxycytidylic acid are effective templates for the polymerization of guanosine 5'-(phospho-2-methylimidazolide). They may be substituted for the corresponding ribo-oligomers without greatly changing the course of the reactions. Since oligomers of deoxynucleotides are much more easily synthesized than the ribo-oligomers, this finding, if it proves general, should greatly facilitate the study of the template properties of oligomers containing two or more bases. Oligodeoxycytidylates facilitate the synthesis of oligoguanylates up to one residue longer than the template in high yield, and oligoguanylates up to twice the length of the template in significant yield. The time-course and regiospecificity of these reactions suggest that "sliding" and "double-templating" are important factors in determining the pattern of reaction products.

Influence of solutes in plasma on the total CO2 content determination: implications for clinical disorders

The purpose of these experiments was to determine the effect of non-aqueous solids on the total CO2 content of plasma. Two major groups of compounds were explored; those which reduced the total CO2 content, such as saline, and those which did not, such as albumin. To assess the former, sufficient sodium chloride was added to a bicarbonate solution gassed with 5% CO2 to increase the total volume by 10%. The total CO2 content fell the predicted 10% from 27.2 to 24.5 mmol/L when sodium chloride was added. In contrast, when the aqueous volume of a bicarbonate solution gassed with 5% CO2 was decreased by isohydric albumin, the total CO2 content was not reduced. We hypothesize that carbamino-compounds were formed with albumin and this raised the volume of CO2 released by an excess of acid. Therefore, the calculated pK' for the bicarbonate buffer system, which is derived from solutions lacking proteins, is not solely determined by the concentrations of bicarbonate, dissolved CO2, carbonate and carbonic acid when albumin is present. The clinical implications of these results will be discussed.

Effect of acute changes in the PaCO2 on acid-base parameters in normal dogs and dogs with metabolic acidosis or alkalosis

There is a linear relationship between the PaCO2 and blood hydrogen ion concentration in normal dogs, but for theoretical reasons to be discussed, we questioned whether this relationship would apply in animals with metabolic acidosis or alkalosis. To study this in more detail, animals were divided into three groups: normal, metabolically acidotic, and metabolically alkalotic. Following anesthesia and bilateral ureteral ligation, dogs were intubated and ventilated to produce acute steady state PaCO2 values corresponding to the range observed during disease states. Changes in the volume and electrolyte composition of the gastrointestinal fluid and urine as well as the concentration and distribution of lactate were evaluated in all experiments. We observed the previously described linear relationship between the PaCO2 and blood hydrogen ion concentration in normal dogs, but the slope of the regression line differed significantly from those of dogs with metabolic acidosis and metabolic alkalosis. On the other hand, there was a consistent relationship between the ratio of the PaCO2 values, but not the absolute PaCO2, and the change in the plasma bicarbonate concentration over a wide range of PaCO2 values in all groups of dogs. The chemical basis for these observations will be discussed.

Effect of potassium on distal nephron hydrogen ion secretion in the dog

The purpose of these investigations was to determine whether potassium might influence the DNHS and, if so, to gain insight into the mechanisms involved. Since DNHS is decreased by ECF volume expansion, dogs were studied in both normovolemic and ECF volume-expanded states. DNHS was assessed in vivo by examining the U-B PCO2. In dogs with an expanded ECF volume, the U-B PCO2 at comparable urine bicarbonate concentrations was almost 50% lower than in the normovolemic dogs. Despite hyperkalemia and kaluresis, the U-B PCO2 was minimally affected by potassium infusion in the dogs with an expanded ECF volume. In contrast, in the normovolemic dogs, the U-B PCO2 was much higher before potassium administration and it decreased after potassium infusion to levels comparable to those observed in the dogs with ECF volume expansion. The U-B PCO2 in the normovolemic dogs was inversely related to the rate of potassium excretion when this rate was less than 150 muEq/min. Amiloride, an agent that decreases the electrical gradient favoring DNHS, caused only a small fall in the U-B PCO2 in potassium-loaded dogs with either a normal or an expanded ECF volume. Although other explanations are possible, we favor the hypothesis that the secretion of potassium into the distal nephron led to a reduced rate of hydrogen ion secretion provided that there was a significant avidity for sodium reabsorption.

Studies on the regulation of hydrogen ion secretion in the collecting duct in vivo: evaluation of factors that influence the urine minus blood PCO2 difference

The purpose of these studies was to clarify the basis of the relationship between the urine bicarbonate concentration and the urine minus blood PCO2 difference in alkaline urine (U-B PCO2) and hence shed light on factors that influence hydrogen ion secretion in the collecting duct in vivo. The U-B PCO2 was used to monitor this latter parameter. In dogs with a normal extracellular fluid (ECF) volume, the U-B PCO2 was not primarily influenced by the urine bicarbonate concentration but rather it was related to the rate of sodium excretion. The U-B PCO2 could be abolished by amiloride when the urine bicarbonate concentration was less than 60 mm. At higher urine bicarbonate concentrations, there was a linear correlation between the U-B PCO2 and the urine bicarbonate concentration in normovolemic dogs given amiloride, but the absolute values were lower than they were in normovolemic animals not treated with amiloride. In the dogs with an expanded ECF volume, the U-B PCO2 was lower than it was in the normovolemic animals, and the U-B PCO2 was nor directly related to the urine bicarbonate concentration and not influenced by the rate of sodium excretion. Amiloride had little influence on the U-B PCO2 under these conditions. These results are interpreted to suggest that the magnitude of collecting duct hydrogen ion secretion is determined primarily by the electrical gradient generated by sodium reabsorption in normovolemic dogs and by the intracellular and lumenal hydrogen ion concentrations when the ECF volume is expanded or when active sodium reabsorption is inhibited by amiloride.

Studies on the mechanism whereby acidemia stimulates collecting duct hydrogen ion secretion in vivo

The purpose of these studies was to elucidate the mechanism whereby collecting duct hydrogen ion secretion was augmented by acidemia. The urine minus blood PCO2 difference in alkaline urine (U-B PCO2) was used to evaluate this parameter. In dogs with a normal ECF volume, the U-B PCO2 factored was high, and there was no significant relationship between the U-B PCO2 factored for the urine bicarbonate concentration and the blood hydrogen ion concentrations unless amiloride, an agent that abolishes the transtubular potential difference, was present. In this latter case, the U-B PCO2 was a linear function of the urine bicarbonate concentration, and the U-B PCO2 factored for the urine bicarbonate concentration was directly proportional to the blood hydrogen ion concentration. To extend the pH range considerably, we used lysine to induce bicarbonaturia in dogs with an expanded ECF volume. Amiloride now caused only a small decrease in the U-B PCO2 at any urine bicarbonate concentration, and furthermore, it did not influence the linear relationship between the U-B PCO2 factored for the urine bicarbonate concentration and the blood hydrogen ion concentration. These results suggests that acidemia stimulates collecting duct hydrogen ion secretion by a mechanism that appears to be independent of the amiloride-sensitive component of the U-B PCO2. We speculate that the mechanism might involve an increased intracellular hydrogen ion concentration during acidemia.

Implications of the finding of calcium carbonate in rabbit urine with respect to renal acidification

Formation of calcium carbonate or carbamino compounds in a bicarbonate solution should generate hydrogen ions and thereby elevate the PCO2 of that solution. The presence of these substances in rabbit urine was established by demonstrating a significantly lower value for urine total carbon dioxide content measured by microgasometry (number of moles) than with the titration technique (number of equivalents). As there was a significant correlation between the calcium and the carbonate contents in the urine, we surmised that most of the carbonate was in the form of a suspension of calcium carbonate. Direct analysis of precipitates from rabbit bladders confirmed this impression. The formation of calcium carbonate in a solution should raise the PCO2 by the reaction: Ca2+ + 2HCO3- leads to CaCO3 + H2CO3 with subsequent dehydration of the H2CO3. In vitro studies demonstrated that the addition of 1 mmol calcium to 1 L of a 200 mM bicarbonate solution raised the PCO2 by approximately 50 mmHg (1 mmHg = 133.322 Pa). However, in vivo measurements of the PCO2 of rabbit urine containing a similar quantity of calcium carbonate revealed that there was no such rise in vivo (urine values = blood values). Therefore, the formation of calcium carbonate should have occurred at an earlier site in the nephron, thereby allowing the PCO2 to diffuse into peritubular capillaries during transit through the nephron.

Evaluation of the effect of pentobarbitone anaesthesia on the plasma potassium concentration in the rabbit and the dog

The purpose of these studies was to determine the reasons for the hypokalaemia observed in rabbits studied in our laboratory. The rabbits consumed standard rabbit chow which is rich in potassium and remained in potassium balance. Hypokalaemia was only observed following anaesthesia. A number of additional investigations were undertaken to clarify the mechanisms involved. The hypokalaemia could not be attributed to technical factors, alkalaemia, hyperinsulinaemia or hyperaldosteronism, but seemed to be a function of anaesthesia. This effect of pentobarbitone anaesthesia was not unique to the rabbit, as similar changes also occurred in the anaesthetized dog. The findings reported in this paper have significant implications with respect to the interpretation of plasma potassium concentrations in anaesthetized subjects or animals.

Comprehensive analysis of urinary metabolites of N'-nitrosonornicotine

A detailed study of the urinary metabolites of N'-nitrosonornicotine has been performed, employing a simple high pressure liquid chromatographic method. The percentage excretion of the principal urinary metabolites was determined over a dose range of 3-300 mg/kg in the F-344 rat, as follows: 4-hydroxy-4-(3-pyridyl)butyric acid (37.1-53.3%, respectively, of the dose), N'-nitrosonornicotine-I-N-oxide (6.7-10.7%), norcotinine (3.2-5.1%), 4-oxo-4-(3-pyridyl)butyric acid (31.1-12.8%), N'-nitrosonornicotine (3.3-5.2%). In the strain A mouse and Syrian golden hamster, the urinary metabolites were qualitatively similar to those observed in the F-344 rat. The interrelationships of the various metabolites of N'-nitrosonornicotine which have been observed in vitro and in vivo were established. The in vitro metabolites resulting from 2'-hydroxylation by liver microsomes, myosmine and 4-hydroxy-I-(3-pyridyl)-1-butanone were converted, by the F-344 rat, primarily to 4-oxo-4-(3-pyridyl)butyric acid as a urinary metabolite. The in vitro metabolite resulting from 5'-hydroxylation by liver microsomes, 2-hydroxy-5-(3-pyridyl)tetrahydrofuran, gave 4-hydroxy-4-(3-pyridyl)butyric acid as its major urinary metabolite, apparently via 5-(3-pyridyl)-tetrahydrofuran-2-one. N'-nitrosonornicotine-I-N-oxide, the remaining major in vitro metabolite, was excreted to a large extent unchanged in F-344 rat urine. The urinary metabolites from 2'-hydroxylation and 5'-hydroxylation of N'-nitrosonornicotine, 4-oxo-4-(3-pyridyl)butyric acid and 4-hydroxy-4-(3-pyridyl)butyric acid, respectively, were not formed from the in vivo metabolite norcotinine and were ot interconverted significantly by the F-344 rat. Thus, these metabolites appear to be reliable indicators for the two possible in vivo alpha-hydroxylations of N'-nitrosonornicotine.

Metabolism in the F344 rat of 4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone, a tobacco-specific carcinogen

The metabolism of the tobacco-specific carcinogen, 4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK), was studied in the F344 rat, in which it induces tumors of the nasal cavity, liver, and lung. When NNK was incubated with rat liver microsomes and a reduced nicotinamide adenine dinucleotide phosphate-generating system, metabolites resulting from alpha-hydroxylation, carbonyl reduction, and N-oxidation were isolated. alpha-Hydroxylation at the methylene carbon gave 4-oxo-4-(3-pyridyl)butanal, whereas alpha-hydroxylation at the methyl carbon gave myosmine and 4-hydroxyl-1-(3-pyridyl)butan-1-one. The formation of these products involved the intermediacy of electrophilic diazohydroxides or carbonium ions which may be proximate or ultimate carcinogens of NNK. Carbonyl reduction gave 4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)butan-1-ol and N-oxidation yielded 4-(N-methyl-N-nitrosamino)-1-(3-pyridyl-N-oxide)-1-butanone. When rats were gavaged with NNK, the microsomal products of alpha-hydroxylation were not detected in the 48-hr urine. Compounds which presumably resulted from further oxidation or reduction of these products, 4-oxo-4-(3-pyridyl)butyric acid, 4-hydroxy-4-(3-pyridyl)butyric acid, and 4-hydroxy-1-(3-pyridyl)butan-1-ol, were isolated. 4-(N-Methyl-N-nitrosamino)-1-(3-pyridyl)butan-1-ol and 4-(N-methyl-N-nitrosamino)-1-(3-pyridyl-N-oxide)-1 butanone were also urinary metabolites.

Metabolic beta-hydroxylation and N-oxidation of N'-nitrosonornicotine

3'-Hydroxy-N'-nitrosonornicotine (2), 4'-hydroxy-N'-nitrosonornicotine (3), N'-nitrosonornicotine 1-N-oxide (4) were synthesized and identified as metabolites in the F-344 rat of the tobacco-specific carcinogen N'-nitrosonornicotine (1). For the synthesis of 2, myosmine (5) was converted to 3'-bromomyosmine (6). Displacement by acetate and hydrolysis gave 3'-hydroxymyosmine (7), which was reduced and nitrosated to give 2. 4'-Hydroxymyosmine (13), the precursor to 3, was prepared by ammonolysis of 1,2-epoxy-4-(N-morpholino)-4-(3-pyridyl)-4-cyanobutane (10). N'-Nitrosonornicotine 1-N-oxide (4) was prepared by m-chloroperbenzoic acid oxidation of 1. When 1 was incubated with liver microsomes from Aroclor-pretreated F-344 rats, trace amounts of 2 and 3 were produced and 4 was a major metabolite. The urine from rats treated with N'-nitrosonornicotine-2'-14C contained only trace amounts of 2 and 3, whereas 4 accounted for 6.7-9.4% of the dose.

Comparative carcinogenicity in F344 rats of the tobacco-specific nitrosamines, N'-nitrosonornicotine and 4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone

The tobacco-specific carcinogens, N'-nitrosonornicotine (NNN) and 4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK), were tested for carcinogenicity in F344 rats. Each nitrosamine in trioctanoin was administered by s.c. injection to 12 male and 12 female rats over a period of 20 weeks. The total dose of each nitrosamine was 3.4 mmol. The experiment was terminated after 12 months. NNK induced nasal cavity tumors in 83% of the males and in 83% of the females, liver tumors in 83% of the males and in 100% of the females, and lung tumors in 67% of the males and in 67% of the females. NNN induced nasal cavity tumors in 92% of the males and in 75% of the females. Only one liver tumor and no lung tumors were observed in the NNN-treated rats. These results indicate that, in the F344 rat, NNK is a more powerful carcinogen than is NNN.

Metabolism of the tobacco specific nitrosamines, N'-nitrosonornicotine and 4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone

The metabolism, in the F-344 rat, of the tobacco-specific carcinogens, N'-nitrosonornicotine (NNN) and 4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK) was studied. NNN was hydroxylated at each position of the pyrrolidine ring; 2'-hydroxylation gave 4-hydroxy-1-(3-pyridyl)-1-butanone in vitro and the corresponding acid in vivo, 3'-hydroxylation gave 3'-hydroxyNNN, 4'-hydroxylation gave 4'-hydroxy-NNN and 5'-hydroxylation gave 4-hydroxy-4-(3-pyridyl)butanal (in vitro) and 4-hydroxy-4-(3-pyridyl) butanoic acid (in vivo). The principle ring hydroxylation in the untreated F-344 rat was 5'-hydroxylation. Pyridine N-oxidation was also observed, giving NNN-1-N-oxide as a major metabolite. The principle urinary metabolites of NNN were formed by 5'-hydroxylation and pyridine-N-oxidation. For NNK, a major process was reduction of the carbonyl to give 4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanol. alpha-Hydroxylation of both the N-methyl and N-methylene groups was also observed, as was formation of NNK-N-oxide in vitro and in vivo.

High pressure liquid chromatographic assay for alpha hydroxylation of N-nitrosopyrrolidine by isolated rat liver microsomes

A high-pressure liquid chromatographic assay for alpha hydroxylation of N-nitrosopyrrolidine by isolated hepatic microsomes was developed. Mixtures consisting of N-nitrosopyrrolidine, microsomes, and an NADPH-generating system were incubated at 37 degrees. The major product of alpha hydroxylation of N-nitrosopyrrolidine, 2-hydroxytetrahydrofuran, was trapped by the addition of 2,4-dinitrophenylhydrazine reagent to form 4-hydroxybutyraldehyde-2,4-dinitrophenylhydrazone. The latter was quantified by reverse-phase high-pressure liquid chromatography. Under optimal conditions, as determined by varying protein and substrate concentrations, the alpha hydroxylation of N-nitrosopyrrolidine was linear for at least 90 min and showed characteristics typical of the microsomal mixed-function oxidase system, such as inhibition by CO and induction by pretreatment of male F-344 rats with Aroclor. N-Nitrosopyrrolidine exhibited type II spectral changes upon interaction with isolated hepatic microsomes. A close correspondence between binding affinity and alpha hydroxylation of N-nitrosopyrrolidine was observed.

Tobacco-specific nitrosamines: formation from nicotine in vitro and during tobacco curing and carcinogenicity in strain A mice

The formation of tobacco-specific nitrosamines from the major tobacco alkaloid nicotine was examined. Detached leaf tobacco was fed either [2'-14C]nicotine or [2'-14C]nornicotine and air cured. The cured leaf was then analyzed for [2'-14C]N'-nitrosonornicotine ([2'-14C]NNN). The yield of [2'-14C]NNN was 0.007% from nornicotine and 0.009% from nicotine. Because the ratio of nicotine to nornicotine in conventional nicotine-type tobacco is 20-100:1, nicotine is considered to be the major precursor for the carcinogen NNN in tobacco. The formation of other nitrosamines from nicotine in vitro was then studied. Reaction of nicotine with NaNO2 gave rise to NNN, as well as to two other nitrosamines, 4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and 4-(N-methyl-N-nitrosamino)-4-(3-pyridyl)butanal (NNA). Analysis of market products revealed the presence of NNK (0.6-24 microgram/g) in chewing tobacco and snuff. The tumorigenic activity of NNN, NNK, and NNA in strain A mice was studied. NNK induced more lung adenomas per mouse than did NNN, whereas NNA was less active than NNN. In addition, two cases of undifferentiated carcinoma of the salivary glands occurred in the NNN experimental groups.

Evidence for metabolic alpha hydroxylation of N-nitrosopyrrolidine

Metabolic alpha hydroxylation of cyclic nitrosamines is important in the activation of these compounds to their ultimate carcinogenic forms. Direct evidence for this process is presented. Both alpha-hydroxynitrosopyrrolidine and 3-formyl-1-propanediazohydroxide, which are unstable intermediates resulting from alpha hydroxylation of nitrosopyrrolidine, were generated inaqueous solution from the stable precursors alpha-acetoxynitrosopyrrolidine and 4-(N-carbethoxy-N-nitrosamino)butanal. The major product resulting from the decomposition of slpha-hydroxynitrosopyrrolidine and 3-formyl-1-propanediazohydroxide was 2-hydroxytetrahydrofuran, the cyclic hemiacetal of 4-hydroxy-butyraldehyde. The same product was isolated as its dinitrophenylhydrazone derivative after incubation of rat liver microsomes with nitrosopyrrolidine and after treatment of rats with nitrosopyrrolidine.

Chemical studies on tobacco smoke LVI. Tobacco specific nitrosamines: origins, carcinogenicity and metabolism

Tobacco contains specific carcinogenic nitrosamines which are derived from nicotine. These compounds may be among the causative agents for the various cancers (lung, oral cavity, oesophagus, bladder and pancreas) which are associated with tobacco usage. The major tobacco specific nitrosamine is N'-nitrosonornicotine (NNN), which has been detected in both unburned tobacco (0.3-90.6 ppm) and cigarette mainstream smoke (137-238 ng/cig.). Studies with labelled precursors showed that the major source of NNN formed during curing of tobacco was nicotine, rather than nornicotine. The transfer rate of NNN from tobacco to mainstream smoke was 11.3%; about half the NNN present in smoke therefore originated from tobacco, with the remainder being formed during smoking. Model studies of the reaction of nicotine and nitrite showed that, in addition to NNN, two other nitrosamines, 4-(N-methyl-N-nitrosamino)-4-(3-pyridyl)-1-butanal (NNA) and 4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK) were formed. Analysis of tobacco revealed the presence of NNK in chewing tobacco and snuff (0.6-2.4 ppm). A comparative bioassay of NNN, NNK and NNA in strain A mice indicated that NNK was more tumorigenic than NNN and that NNA was inactive. NNN, which had previously been shown to induce oesophageal and nasal cavity tumours in rats, also was a moderately active carcinogen in the Syrian golden hamster, giving tracheal tumours. A study of the metabolism of cyclic nitrosamines was initiated. Metabolic alpha-hydroxylation of nitrosopyrrolidine, which is thought to be the critical step in activation of this compound, was demonstrated by detection in vitro and in vivo of 2-hydroxytetrahydrofuran, which was the product of decomposition of alpha-hydroxynitrosopyrrolidine. The metabolism of the related cyclic nitrosamine, NNN, is currently under investigation, with emphasis on metabolites resulting from alpha- and beta-hydroxylation. These analytical and metabolic studies are intended to clarify the possible relationship of tobacco-specific nitrosamines and site-specific cancers in tobacco users.