Evidence for a non-orthostatic origin of orthostatic tremor

OBJECTIVES

Orthostatic tremor was first described by Heilman in 1984. It usually occurs in the legs during stance and decreases markedly during sitting or walking. The aim of this study was to determine if orthostatic tremor is invariably associated with the orthostatic and weight bearing conditions in the arms and legs, and to investigate the features of orthostatic tremor under different levels of peripheral loading.

METHODS

Multichannel surface EMG recordings were obtained under different conditions (body posture and peripheral loading) from the proximal arm and leg muscles of seven patients fulfilling the clinical and electrophysiological criteria of orthostatic tremor.

RESULTS

In weight bearing positions (stance; weight bearing on the hands on all fours), all patients showed 13 Hz-16 Hz tremor activity, predominantly in the active limb. No tremor activity could be found in a supine position with muscles at rest. Isometric contraction of the limbs in the supine position led to synchronous 13 Hz-16 Hz rhythmic activity in five patients. No tremor was seen when the subjects were suspended in a harness with relaxed legs. Isometric contraction of the legs in this position produced tremor in two patients. A stepwise reduction of the body weight by a harness reduced the tremor activity. Additional loading (10 kg-20 kg) during stance led to an increase in tremor amplitude, but tremor frequency remained unchanged.

CONCLUSIONS

Orthostatic tremor is invariably present during stance or other weight bearing positions. It is not, however, always associated with orthostasis. In at least some patients it can be classified as an orthostasis independent action tremor. The failure of peripheral loading to modify tremor frequency indicates that orthostatic tremor may have a central, rather than a peripheral, origin.

EMAP II: a modulator of neovascularization in the developing lung

Neovascularization is a key regulatory process in fetal growth and development. Although factors promoting growth and development of the pulmonary vasculature have been investigated, nothing is known regarding the molecular mechanisms that may counteract these stimuli. Endothelial monocyte-activating polypeptide (EMAP) II has recently been identified as an antiangiogenic factor in tumor vascular development. We postulated that EMAP II is a putative negative modulator of lung vascular growth. EMAP II mRNA and protein decrease fivefold (P < 0.01) as the developing lungs in the fetal mouse progress from having poor vascularization (day 14) to having complete vascular development at term (day 18.5). EMAP II protein expression continues to remain low throughout postnatal life and into adulthood, with the exception of a surge that correlates with microvascular maturation. Furthermore, through the use of in situ hybridization and immunohistochemistry, EMAP II is localized throughout the lung, with significant expression in the submyoepithelial area during the early stages of lung development when there is minimal vascular development. In contrast, EMAP II is distributed around the large vessels during the end of vascular development, suggesting that EMAP II modulates the neovascularization process. We speculate that EMAP II is a director of neovascularization in the developing lung.

[Neuroprotection in stroke. A critical overview]

Cerebral ischemia leads to a cascade of pathophysiological processes which contribute to ischemic cell damage. In addition to the excitotoxicity, which is characterized by a massively elevated extracellular concentration of excitatory amino acids and an intracellular overload with calcium, the increased formation of free radicals, the inflammation and the apoptosis are also involved in ischemic damage. Neuroprotection, a pharmacological interaction with these pathophysiological processes, is one possibility to attenuate the consequences of cerebral ischemia. In experimental studies it could be demonstrated that glutamate antagonists, calcium antagonists or radical scavengers reduce the ischemic damage. Substances which interact with inflammation or apoptosis have also been shown to be protective. Clinical trials, however, showed no beneficial effects. This discrepancy is mainly due to differences in the design of the studies. In experimental studies the substances were often applied before or at the onset of ischemia, the survival time after ischemia was very short and the effects of neuroprotection were mainly evaluated by morphological examinations. Considering these points in future preclinical studies it is hoped that neuroprotective substances will be found which may be effective in clinical trials.

Inhibition of transforming growth factor beta1-induced hepatoma cell apoptosis by liver tumor promoters: characterization of primary signaling events and effects on CPP32-like caspase activity

The effects of the liver tumor promoters phenobarbital, clofibrate, dieldrin, and DDT on transforming growth factor-beta1 (TGFbeta)-induced apoptosis were studied in FTO-2B hepatoma cells. Inhibition of apoptosis by these compounds was strongly correlated with a decrease in CPP32-like caspase activity. Similar effects were obtained with insulin and dexamethasone. CPP32-like activity may thus provide a useful tool for quantiation of apoptosis under various treatment conditions. Diverse effects on apoptosis-associated cellular signaling proteins were observed: insulin led to an activation of the MAP kinases ERK1/2, of PKB/Akt and of NF-kappaB, phenobarbital and clofibrate enhanced NF-kappaB activity solely, while dexamethasone slightly enhanced NF-kappaB activity and increased the expression of Bcl-xL. Since inhibition of apoptosis was still detectable if the anti-apoptotic compounds were administered more than 10 h after TGFbeta, the diverse primary signals appear to converge at a presumably late stage of apoptosis, but upstream of activation of CPP32 or related caspases.

Characterization of human Kv4.2 mediating a rapidly-inactivating transient voltage-sensitive K+ current

A human cDNA for the voltage-sensitive potassium channel subunit Kv4.2 has been cloned and functionally characterized. The human Kv4.2 (KCND2) gene was mapped at 7q31-32. Kv4.2 mRNA is prominently expressed in human brain. Relatively high concentrations of Kv4.2 mRNA occurred in mRNA preparations of amygdala, caudate nucleus, cerebellum, hippocampus, substantia nigra, and thalamus. Kv4.2 mRNA was not detected in human heart, kidney, liver, lung, pancreas, and skeletal muscle. The derived Kv4.2 open reading frame consists of 630 amino acids. In comparison to rat Kv4.2, the human Kv4.2 sequence is highly conserved showing amino acid sequence differences at five positions only. The Kv4.2 subunits were expressed heterologously in human embryonic kidney (293) cells and mediated a rapidly inactivating, A-type outward K+ current. The gating kinetics of the Kv4.2-mediated currents were very similar to those of rat Kv4.2-mediated currents. Both the Kv4.2 and Kv4.3 subunits have been implicated in mediating the transient outward K+ current Ito in rodent cardiac myocytes. In contrast we did not detect Kv4.2. but solely Kv4.3 mRNA in human heart RNA preparations. This may suggest that Kv4.2 subunits do not contribute to the rapid transient outward K+ current of atrial and ventricular myocytes in humans.

Automatic acquisition of fiducial markers and alignment of images in tilt series for electron tomography

Three-dimensional reconstruction of a section of biological tissue by electron tomography requires precise alignment of a series of two-dimensional images of the section made at numerous successive tilt angles. Gold beads on or in the section serve as fiducial markers. A scheme is described that automatically detects the position of these markers and indexes them from image to image. The resulting set of position vectors are arranged in a matrix representation of the tilt geometry and, by inversion, alignment information is obtained. The scheme is convenient, requires little operator time and provides an accuracy of < 2 pixels RMS. A tilt series of 60-70 images can be aligned in approximately 30 min on any modern desktop computer.

Spontaneous splenic rupture in infectious mononucleosis: conservative management with gradual percutaneous drainage of a subcapsular hematoma

Spontaneous splenic rupture (SSR) is a rare but potentially lethal complication of infectious mononucleosis (IM). Because the inflamed spleen is usually enlarged, congested, and friable, emergency splenectomy is recommended. We describe the conservative management of a SSR in a 16-year-old boy with IM. A pigtail catheter was inserted under ultrasonographic guidance and left in place for 36 h. This allowed the successful evacuation of the hematoma without compromising the splenic parenchyma.

Functional analysis of the human cytochrome P4501A1 (CYP1A1) gene enhancer

The environmental contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD or dioxin) induces gene transcription, a process that requires binding of the activated aryl hydrocarbon receptor (AhR) to dioxin-responsive elements (DREs) within the enhancer region of responsive genes. Most of what is known about the molecular mechanism of AhR-dependent gene activation results from studies on the murine prototype TCDD-responsive gene cytochrome P4501A1 (CYP1A1). Much less is known, however, about the regulation of human TCDD-responsive genes. We have therefore conducted a detailed analysis of the enhancer region of the human CYP1A1 gene. From the ten DRE core motifs investigated within a stretch of 1400 bp in two human tumor cell lines using a ligation-mediated PCR technique, five motifs displayed a TCDD-inducible in vivo footprint. Four of these sites were functional enhancer sequences as demonstrated by a transient expression assay. Based on these data, a distinct functional consensus sequence for DRE motifs within the human CYP1A1 gene is suggested. After introduction of the four functional sites into various mouse hepatoma cell lines, only three exhibited a functional response, suggesting some species differences in CYP1A1 gene regulation. In addition to the footprints at DRE sites, we also detected protein-DNA interactions at three G-rich domains located within the enhancer region of the human CYP1A1 gene. Our data show that, besides some similarities in the regulation of the human and mouse CYP1A1 genes, there also exist some distinct differences, including number, location, and functional consensus sequences of DRE motifs, as well as quantity and location of footprinted G-rich domains.

Induction of fibrinogen binding and platelet aggregation as a potential intrinsic property of various glycoprotein IIb/IIIa (alphaIIbbeta3) inhibitors

The blockade of platelet integrin glycoprotein (GP) IIb/IIIa is a promising new antiplatelet strategy. The binding of ligands or of the ligand-mimetic peptide RGD causes a conformational change of GP IIb/IIIa from the nonactivated to the activated state. Because several blocking agents/inhibitors are ligand-mimetics, the current study evaluates whether these agents have the intrinsic property to activate GP IIb/IIIa. Fibrinogen binding to GP IIb/IIIa on platelets or on CHO cells expressing recombinant GP IIb/IIIa was evaluated by flow cytometry or 125I-labeled fibrinogen. Incubation with the monoclonal antibody (MoAb) fragment c7E3 (abciximab) results in fibrinogen binding to GP IIb/IIIa and in the access of ligand-induced binding sites. At low concentrations (0.01 to 0.1 microgram/mL), this intrinsic activating property of c7E3 can result in platelet aggregation. The disintegrin flavorodin and the RGD analogue fradafiban also induce fibrinogen binding, whereas the blocking MoAbs 2G12 and P2 and the activation-specific MoAb PAC-1 do not. Aspirin and indomethacin cannot block c7E3-induced fibrinogen binding to GP IIb/IIIa, but can inhibit c7E3-induced platelet aggregation. Thus, we conclude that GP IIb/IIIa inhibitors can demonstrate an intrinsic activating property, which can result in fibrinogen binding to GP IIb/IIIa and consequently in platelet aggregation. Cyclooxygenase inhibitors can inhibit platelet aggregation caused by GP IIb/IIIa inhibitors. Further studies will have to evaluate the clinical relevance of the potential intrinsic activating property of GP IIb/IIIa inhibitors and define consequences for the future drug development and evaluation of these potent antiplatelet agents.

Identification of a new inborn error in bile acid synthesis: mutation of the oxysterol 7alpha-hydroxylase gene causes severe neonatal liver disease

We describe a metabolic defect in bile acid synthesis involving a deficiency in 7alpha-hydroxylation due to a mutation in the gene for the microsomal oxysterol 7alpha-hydroxylase enzyme, active in the acidic pathway for bile acid synthesis. The defect, identified in a 10-wk-old boy presenting with severe cholestasis, cirrhosis, and liver synthetic failure, was established by fast atom bombardment ionization-mass spectrometry, which revealed elevated urinary bile acid excretion, a mass spectrum with intense ions at m/z 453 and m/z 510 corresponding to sulfate and glycosulfate conjugates of unsaturated monohydroxy-cholenoic acids, and an absence of primary bile acids. Gas chromatography-mass spectrometric analysis confirmed the major products of hepatic synthesis to be 3beta-hydroxy-5-cholenoic and 3beta-hydroxy-5-cholestenoic acids, which accounted for 96% of the total serum bile acids. Levels of 27-hydroxycholesterol were > 4,500 times normal. The biochemical findings were consistent with a deficiency in 7alpha-hydroxylation, leading to the accumulation of hepatotoxic unsaturated monohydroxy bile acids. Hepatic microsomal oxysterol 7alpha-hydroxylase activity was undetectable in the patient. Gene analysis revealed a cytosine to thymidine transition mutation in exon 5 that converts an arginine codon at position 388 to a stop codon. The truncated protein was inactive when expressed in 293 cells. These findings indicate the quantitative importance of the acidic pathway in early life in humans and define a further inborn error in bile acid synthesis as a metabolic cause of severe cholestatic liver disease.

Neurophysiological abnormalities in the Westphal variant of Huntington's disease

The Westphal variant of Huntington's disease (HD) is a distinct clinical entity of HD characterized by a rigid-hypokinetic syndrome and is often associated with a juvenile onset of disease. Definite genetic differences between the subtypes of HD have not been delineated so far. Here we present the results of a battery of neurophysiological tests including somatosensory-evoked potentials, blink reflexes, long-latency reflexes, and measurement of saccadic velocities in a Westphal HD patient. Although quantitative assessment of his motor performance showed a severe hypokinetic syndrome resembling Parkinson's disease, the results of somatosensory-evoked potentials and blink reflexes were indistinguishable from results obtained in hyperkinetic HD patients. Long-latency reflexes, however, which are typically absent in hyper-kinetic HD patients, were retained in this patient. It is concluded that neurophysiology in HD patients is not a mere reflection of the patient's symptomatology but can give insight into the underlying pathophysiological process.

Gender-related differences in bile acid and sterol metabolism in outbred CD-1 mice fed low- and high-cholesterol diets

These studies were undertaken to determine whether in young adult outbred CD-1 mice there were any gender-related differences in basal bile acid metabolism that might be important in determining how males and females in this species responded to a dietary cholesterol challenge. When fed a plain cereal-based rodent diet without added cholesterol, 3-month-old females, compared with age-matched males, manifested a significantly larger bile acid pool (89.1 vs. 54.1 micromol/100 g body weight), a higher rate of fecal bile acid excretion (13.6 vs. 8.5 micromol/d/100 g body weight), a more efficient level of intestinal cholesterol absorption (41.1% vs. 25. 3%), and a lower rate of hepatic sterol synthesis (338 vs. 847 nmol/h/g). Similar results were found in C57BL/6 and 129Sv inbred mice. In matching groups of CD-1 mice fed a diet containing 1% cholesterol for 21 days, hepatic cholesterol levels increased much more in the females (from 2.4 to 9.1 mg/g) than in the males (from 2. 1 to 5.2 mg/g). This occurred even though the level of stimulation of cholesterol 7-hydroxylase activity in the females (79%) exceeded that in the males (55%), as did the magnitude of the increase in fecal bile acid excretion (females: 262% vs. males: 218%). However, in both sexes, bile acid pool size expanded only modestly and by a comparable degree (females: 19% vs. males: 26%) so that in the cholesterol-fed groups, the pool remained substantially larger in the females than in the males (102.3 vs. 67.6 micromol/100 g body weight). Together, these data demonstrate that while male and female CD-1 mice do not differ qualitatively in the way cholesterol feeding changes their bile acid metabolism, the inherently larger bile acid pool in the female likely facilitates the delivery of significantly more dietary cholesterol to the liver than is the case in males, thereby resulting in higher steady-state hepatic cholesterol levels.

In vivo and in vitro induction of c-fos in avian exocrine salt gland cells

Osmotic stress in ducklings (Anas platyrhynchos) results in salt secretion and adaptive cell proliferation and differentiation in the nasal glands. We investigated whether osmotic stress in vivo or muscarinic ACh receptor activation in vitro changed the expression levels of the cellular protooncogene products Fos and Jun, which may play a role in the initiation of the adaptive processes. Using Fos- and Jun-specific polyclonal antisera in Western blot experiments, we demonstrated that Jun is constitutively expressed in nasal gland tissue, whereas Fos is not detectable in tissue from unstressed (naive) animals. Under conditions of osmotic stress imposed by replacing the drinking water of the animals with a 1% NaCl solution, Jun protein remains constant in nasal gland tissue, whereas Fos protein is transiently upregulated. Treatment of cultured nasal gland tissue with muscarinic agonists results in a transcriptionally regulated expression of Fos in an atropine-sensitive manner. Immunohistochemical experiments show that Fos accumulation occurs in the nuclei of the secretory cells. These results indicate that the activation of the c-fos gene induced by muscarinic ACh receptor-mediated signaling pathways may play an important role in the initiation of adaptive growth and differentiation processes in nasal glands of osmotically stressed ducklings.

Mutations of the cystic fibrosis gene in patients with chronic pancreatitis

BACKGROUND

The pancreatic lesions of cystic fibrosis develop in utero and closely resemble those of chronic pancreatitis. Therefore, we hypothesized that mutations of the cystic fibrosis transmembrane conductance regulator (CFTR) gene may be more common than expected among patients with chronic pancreatitis.

METHODS

We studied 134 consecutive patients with chronic pancreatitis (alcohol-related disease in 71, hyperparathyroidism in 2, hypertriglyceridemia in 1, and idiopathic disease in 60). We examined DNA for 22 mutations of the CFTR gene that together account for 95 percent of all mutations in patients with cystic fibrosis in the northwest of England. We also determined the length of the noncoding sequence of thymidines in intron 8, since the shorter the sequence, the lower the proportion of normal CFTR messenger RNA.

RESULTS

The 94 male and 40 female patients ranged in age from 16 to 86 years. None had a mutation on both copies of the CFTR gene. Eighteen patients (13.4 percent), including 12 without alcoholism, had a CFTR mutation on one chromosome, as compared with a frequency of 5.3 percent among 600 local unrelated partners of persons with a family history of cystic fibrosis (P<0.001). A total of 10.4 percent of the patients had the 5T allele in intron 8 (14 of 134), which is twice the expected frequency (P=0.008). Four patients were heterozygous for both a CFTR mutation and the 5T allele. Patients with a CFTR mutation were younger than those with no mutations (P=0.03). None had the combination of sinopulmonary disease, high sweat electrolyte concentrations, and low nasal potential-difference values that are diagnostic of cystic fibrosis.

CONCLUSIONS

Mutations of the CFTR gene and the 5T genotype are associated with chronic pancreatitis.

IFN-gamma induces the high-affinity Fc receptor I for IgG (CD64) on human glomerular mesangial cells

The deposition of immune complexes, followed by activation of complement and/or Fc receptors and generation of chemoattractants, is the most common feature of human glomerulonephritis. Recently we have shown that primary cultured human glomerular mesangial cells (HMC), which are normally negative for IgG Fc receptors, can be stimulated to express the low-affinity FcgammaRIII-A receptor isoform. In this study we further demonstrate that activation of HMC through IFN-gamma resulted in the functional expression of the high-affinity Fc receptor for IgG (FcgammaRI, CD64). IFN-gamma-dependent induction of classical FcgammaRIa1 mRNA as well as a2, b2 splice variants were evident after 24 h in proliferating HMC and after 48 h in resting HMC. Transcription of FcgammaRI mRNA was also induced by IL-10 in proliferating HMC, whereas other cytokines such as IL-3, transforming growth factor-beta1 and granulocyte-macrophage colony-stimulating factor were not effective. Cell surface expression of FcgammaRI could be detected by flow cytometric analysis after IFN-gamma stimulation and was accompanied by the augmentation of MHC class II and the up-regulation of intercellular adhesion molecule-1 expression. Triggering of HMC by cross-linking FcgammaRI with F(ab')2 fragments of the anti-CD64 monoclonal antibody 22 led to enhanced synthesis of mRNA for the chemokines IL-8 and monocyte chemoattractant protein-1, indicating that the FcgammaRI of HMC is functionally active. These in vitro data suggest that engagement of both FcgammaRI and FcgammaRIII-A on activated HMC through IgG immune complexes may result in an increased chemoattraction of leukocytes into the glomerulus, contributing to the development of glomerulonephritis.

Precision grip and Parkinson's disease

In order to investigate sensorimotor processing and force development in Parkinson's disease, 16 patients, four patients with hemiparkinsonism and 12 age-matched normal subjects were assessed during lifting and holding of an object in a precision grip between thumb and forefinger, or holding the object in this grip at a fixed height above a table. In the former case, object loading could be changed between lifts without warning. In the latter case, unexpected step load changes to the object were applied to the object with a torque motor. All procedures could be applied with or without visual control of the hand and the object. Normal subjects lifted an unpredictable load employing the grip force parameters used in the preceding lift. If a load change was encountered, the parameters became adapted to the new conditions during the lift, modulating grip forces to match the loading. Parkinsonian patients retained this strategy and the ability to regulate grip forces according to load. Under all conditions, however, parkinsonian subjects developed abnormally high grip forces in both the lift and the hold phase, although the ratio of these forces remained normal. Lifting height was normal in parkinsonian subjects, but the duration of the lifting task was significantly prolonged, due to a marked slowing in the rate of grip force development in the lead-up to object lift-off and to prolongation of the movement phase. Forewarning of object loading, with or without visual control, did not reduce timing deficits or improve the rate of grip force development. However, it did allow parkinsonian subjects to reduce the safety margin significantly. Responses to step load changes imposed during holding without visual control showed minor abnormalities in the parkinsonian patients: onset latencies and EMG activity in the first dorsal interosseus and thenar muscles were normal up to 140 ms after displacement. Subsequent EMG activity in the first dorsal interosseus remained largely normal, but activity later in the slip response (140-210 ms), subject to voluntary influence, was reduced in the thenar muscle. Differences were less marked under visual conditions, but remained significant. We concluded that the internal parameter set for lifting an object in a precision grip and the automatic processes adapting precision grip to actual conditions are intact in Parkinson's disease. However, parkinsonian subjects generate abnormally high grip forces and require longer than normal subjects to complete a lift, particularly with lighter loads. This deterioration in performance reflects both reduced effectiveness of sensorimotor processing and impairment in the rate of force development in Parkinson's disease.

MR findings in growth hormone deficiency: correlation with severity of hypopituitarism

BACKGROUND AND PURPOSE

Growth hormone deficiency may present as an isolated deficit (IGHD) or in association with multiple deficiencies (MPHD). Previous studies have not compared the MR imaging findings with the severity of hypopituitarism. Our purpose was to determine whether MR imaging can distinguish between IGHD and MPHD.

METHODS

Forty-four patients with growth hormone deficiency who were examined by MR imaging were included in this retrospective study. On the basis of the endocrinologic findings, 21 were determined to have IGHD and 23 to have MPHD. The presence, size, location, and morphologic characteristics of the stalk, the neurohypophysis, and the adenohypophysis were recorded in each case. Findings in the two groups were compared. Statistical significance was determined by t-test.

RESULTS

The stalk was normal in one patient with IGHD and in none of those with MPHD; it was truncated or thin in 19 patients with IGHD (90%) and in only one with MPHD (4%); it was absent in 22 patients with MPHD (96%) and in only one patient with IGHD (5%). These differences between the two groups were highly significant. In 81% of the IGHD patients and in 91% of the MPHD patients the location of the neurohypophysis was ectopic. This difference between the two groups was not significant. Among IGHD patients, the adenohypophysis was of normal size in 13 patients (62%), small in six (29%), and absent in two (9%); the corresponding findings in MPHD patients were seven (30%), six (26%), and 10 (44%).

CONCLUSION

The majority of IGHD patients had a truncated or thin stalk and a normal or small adenohypophysis. An absent stalk and adenohypophysis are characteristic of MPHD. MR imaging can contribute to the prediction of the pattern and severity of hypopituitarism in patients with growth hormone deficiency.

Marked reduction in bile acid synthesis in cholesterol 7alpha-hydroxylase-deficient mice does not lead to diminished tissue cholesterol turnover or to hypercholesterolemia

These studies used mice that were deficient in cholesterol 7alpha-hydroxylase to determine the effects of reduced bile acid synthesis on cholesterol homeostasis. In mice lacking this enzyme, bile acid synthesis was reduced from 8.3 to 3.4 micromol/day per 100 g body weight, the intestinal bile acid pool was decreased from 62.5 to 13.2 micromol/100 g bw, and the proportion of hyodeoxycholate, relative to cholate, in this pool was significantly increased. Associated with these changes, intestinal cholesterol absorption decreased from 37% to <1% while triacylglycerol absorption and animal weight gain remained essentially unaffected. The very low rate of cholesterol absorption could be corrected by feeding the mutant mice cholate, but not hyodeoxycholate. The reduction in sterol uptake across the intestine was associated with a 2-fold increase in cholesterol synthesis in the small bowel and liver and an increase in fecal neutral sterol excretion from 15.2 to 35.7 micromol/day per 100 g bw. The size of the cholesterol pools in the plasma, various organs and whole animal remained constant. Thus, under circumstances where the excretion of sterol as bile acids was markedly reduced, total cholesterol turnover actually increased from 164 to 239 mg/day per kg bw. This study demonstrates the complex interactions between bile acid and cholesterol metabolism and the dramatic effects of eliminating a single gene product; however, even though a major catabolic pathway was deleted, cholesterol balance across the animal was maintained.

The deoxyxylulose phosphate pathway of terpenoid biosynthesis in plants and microorganisms

Recent studies have uncovered the existence of an alternative, non-mevalonate pathway for the formation of isopentenyl pyrophosphate and dimethylallyl pyrophosphate, the two building blocks of terpene biosynthesis.

Expression of interleukin 6 in the rat striatum following stereotaxic injection of quinolinic acid

Stereotaxic intrastriatal injection of the naturally occurring N-methyl-D-aspartate (NMDA) agonist quinolinic acid (QA) serves as a valuable in vivo model to study excitotoxic cell damage in the central nervous system (CNS). Although morphological changes such as neuronal loss, glial activation and remote reactions following QA injection have been described in some detail, much less is known about the molecular mechanisms mediating the accompanying glial response. Cytokines are known to play a crucial role in almost all kinds of CNS alterations. We now demonstrate that IL-6, a multifunctional glycoprotein which belongs to the family of neurokines, is expressed endogenously in the rat striatum following QA injection. Using Northern blot analysis, a massive but transient upregulation of IL-6 mRNA could be detected. This started 3 h after QA injection, reached a maximum at 6 h and disappeared within 24 h. That activated microglia are the most likely cellular source of the observed corresponding IL-6 protein expression could be concluded by comparing the immunocytochemical pattern of IL-6 expression and microglial activation. Interestingly, astrocytes initially downregulate their expression of glial fibrillary acidic protein (GFAP) in the excitotoxically injured striatum, but show a delayed increase in GFAP immunoreactivity starting in the periphery of the striatum, subsequently expanding to the core. The early transient IL-6 expression may play an important role in initiating the delayed astrocytic response following excitotoxic cell injury.

Expression of hypoxia-inducible genes in tumor cells

Tumor tissue oxygenation impacts on proliferation of cancer cells and their sensitivity towards radio- and chemotherapy. Under low oxygen, mammalian cells show an adaptive response that leads to the induction of a number of genes with well-defined roles in oxygen supply and energy maintenance, e.g. genes encoding enzymes of the glycolytic pathway. The hypoxia-inducible factor 1 (HIF-1), a transcription factor consisting of the two proteins HIF-1alpha and HIF-1beta, plays a major role in the pleiotropic response observed under low oxygen. We have determined, by Northern analysis, the mRNA levels of HIF-1alpha and of two glycolytic enzymes known to be transcriptionally activated by HIF-1, namely phosphoglycerate kinase 1 (PGK 1) and pyruvate kinase M2 (PKM2), in different hepatoma cell lines and in mouse and human tissues. Hypoxic treatment of various mouse and human hepatoma cell lines led to the expected increase in the amount of PGK1 and PKM2 mRNA, while HIF-1alpha mRNA levels were not significantly elevated. Analysis of mouse liver tumors demonstrated no tumor-specific increases in HIF-1alpha or PGK1 mRNA levels. In five of eight human colorectal cancers investigated, PGK1 and PKM2 mRNA levels were increased in comparison to the corresponding normal tissues, while HIF-1alpha mRNA levels were not significantly changed. The majority of the colorectal cancers demonstrated p53 immunoreactivity, presumably due to mutation of the gene; there was, however, no correlation between the p53 staining pattern and mRNA expression levels of glycolytic enzymes.

Social isolation blocks the expression of memory after training that a food is inedible in Aplysia fasciata

Isolating a sexually mature Aplysia fasciata for either 1 or 24 hr immediately after training that a food is inedible blocks the subsequent expression of memory measured 24 hr later. Isolation that is delayed for 1 hr after training, but not for 12 hr after training, is also effective in blocking memory. Isolation affects memory because of a specific effect caused by the absence of pheromones secreted by conspecifics rather than by a nonspecific change in the chemical environment, because transferring animals to a novel environment (120% seawater) that contains a conspecific does not affect memory. Isolation also does not affect memory in sexually immature Aplysia, even though immature animals are able to sense one another's presence. Isolation may affect memory because social (and sexual) isolation is a form of stress in mature A. fasciata, and stress after training affects retention in many animals.