Studies on the biosynthesis of taxol. Synthesis Of taxa-4(20), 11(12)-diene-2alpha,5alpha-diol

The synthesis of taxa-4(20),11(12)-diene-2alpha,5alpha-diol is described. An improved procedure for the intramolecular Diels-Alder cycloaddition previously reported in our synthesis of taxa-4(5), 11(12)-diene has been utilized to prepare a taxoid with oxygenation in the B and C rings. It has been established previously that taxa-4(20),11(12)-dien-5alpha-ol is the first oxygenated intermediate on the biosynthetic pathway to Taxol. Taxa-4(20), 11(12)-diene-2alpha,5alpha-diol (5), which has been observed in a biosynthetic conversion, is a potential candidate as the second oxygenated intermediate on the Taxol biosynthetic pathway, has been prepared to probe the intermediacy of this substance.

Single granule pH cycling in antigen-induced mast cell secretion

The pH cycling of individual granules in secreting (serotonin-loaded) mast cells is quantitatively examined using multicolor multiphoton fluorescence microscopy. A typical exocytosis event consists of maximal calcium rise at time zero, granule alkalization a few seconds later and, finally, complete contents release at a fraction of a second after alkalization. Membrane fusion is either transient, as indicated by subsequent granule reacidification, or ‘full’, as indicated by a granule disappearance with a collapse of its membrane into the plasma membrane. The relative frequency of these two coexisting behaviors (the ‘kiss-to-collapse’ ratio) is approximately 2:1. A typical transiently fusing granule experiences multiple alkalization/acidification cycles after addition of exogenous antigen. Between recycling granules, coalescence events are frequent, with 80% resulting in a collapse of the formed granule complex to the plasma membrane. The full dynamics of secretion encompass a complex combination of these granule activities.

Synthesis and evaluation of microtubule assembly inhibition and cytotoxicity of prenylated derivatives of cyclo-L-Trp-L-Pro

The synthesis of three isoprenylated derivatives of cyclo-L-Trp-L-Pro is described. These substances have been evaluated for cytotoxic activity in rat normal fibroblast 3Y1 cells and have also been evaluated in vitro for the inhibition of microtubule assembly.

Functional instability in non-contact ankle ligament injuries

OBJECTIVES

To measure objectively functional standing balance in the acute stages of non-contact ankle sprain, and to compare patients with controls.

METHODS

A Chattanooga balance machine was used to measure postural stability in patients with acute ankle sprain and uninjured controls over a two week period, in one and two legged stance, with eyes open and closed. Participants also completed the Olerud and Molander questionnaire to provide a subjective measure of ankle function.

RESULTS

There was a highly significant improvement in questionnaire scores for the patients during the study period (p<0.0001). Patients appeared to be less stable than controls in all balance tests, although the difference did not reach significance. There was evidence of improvement over time in the number of tests successfully completed on the injured leg in single legged stance with eyes closed (p = 0.043) between visits 1 and 3.

CONCLUSIONS

The patient group showed a subjective improvement, which supports clinical experience of treating acute ankle injuries. There is some evidence that on average the patient group appeared to be less stable than controls in all balance tests, although the difference did not reach statistical significance, even on the uninjured leg. There is a need to carry out further studies to confirm the results found in this pilot study and to investigate the hypotheses generated. It would be useful to evaluate a simple test that could be used clinically to monitor progress after ankle injury, and also to identify athletes with decreased functional stability, who may be more at risk of sustaining ankle injury.

FR900482 class of anti-tumor drugs cross-links oncoprotein HMG I/Y to DNA in vivo

BACKGROUND

Overexpression of the high-mobility group, HMG I/Y, family of chromatin oncoproteins has been implicated as a clinical diagnostic marker for both neoplastic cellular transformation and increased metastatic potential of several human cancers. These minor groove DNA-binding oncoproteins are thus an attractive target for anti-tumor chemotherapy. FR900482 represents a new class of anti-tumor agents that bind to the minor groove of DNA and exhibit greatly reduced host toxicity compared to the structurally related mitomycin C class of anti-tumor drugs. We report covalent cross-linking of DNA to HMG I/Y by FR900482 in vivo which represents the first example of a covalent DNA-drug-protein cross-link with a minor groove-binding oncoprotein and a potential novel mechanism through which these compounds exert their anti-tumor activity.

RESULTS

Using a modified chromatin immunoprecipitation procedure, fragments of DNA that have been covalently cross-linked by FR900482 to HMG I/Y proteins in vivo were polymerase chain reaction-amplified, isolated and characterized. The nuclear samples from control cells were devoid of DNA fragments whereas the nuclear samples from cells treated with FR900482 contained DNA fragments which were cross-linked by the drug to the minor groove-binding HMG I/Y proteins in vivo. Additional control experiments established that the drug also cross-linked other non-oncogenic minor groove-binding proteins (HMG-1 and HMG-2) but did not cross-link major groove-binding proteins (Elf-1 and NFkappaB) in vivo. Our results are the first demonstration that FR900482 cross-links a number of minor groove-binding proteins in vivo and suggests that the cross-linking of the HMG I/Y oncoproteins may participate in the mode of efficacy as a chemotherapeutic agent.

CONCLUSIONS

We have illustrated that the FR class of anti-tumor antibiotics, represented in this study by FR900482, is able to produce covalent cross-links between the HMG I/Y oncoproteins and DNA in vivo. The ability of this class of compounds to cross-link the HMG I/Y proteins in the minor groove of DNA represents the first demonstration of drug-induced cross-linking of a specific cancer-related protein to DNA in living cells. We have also demonstrated that FR900482 cross-links other minor groove-binding proteins (HMG-1 and HMG-2 in the present study) in vivo; however, since HMG I/Y is the only minor groove-binding oncoprotein presently known, it is possible that these non-histone chromatin proteins are among the important in vivo targets of this family of drugs. These compounds have already been assessed as representing a compelling clinical replacement for mitomycin C due to their greatly reduced host toxicity and superior DNA interstrand cross-linking efficacy. The capacity of FR900482 to cross-link the HMG I/Y oncoprotein with nuclear DNA in vivo potentially represents a significant elucidation of the anti-tumor efficacy of this family of anticancer agents.

Attitudes to emotional expression and personality in predicting post-traumatic stress disorder

OBJECTIVES

To test hypotheses derived from a suggestion of Williams (1989) that negative attitudes towards emotional expression act as a predisposing or maintaining factor for post-traumatic stress reactions following a traumatic event.

DESIGN

The study employed a prospective design in which attitudes to emotional expression, the 'Big Five' personality factors (Costa & McCrae, 1992a) and initial symptoms and injury severity within 1 week of a road traffic accident were used to predict the development of post-traumatic stress disorder 6 weeks post-accident.

METHOD

Sixty victims of road traffic accidents randomly selected from attenders at a large A&E department were assessed by questionnaire and interview. Measures comprised a 4-item scale relating to emotional expression, standardized scales for intrusion and avoidance features of traumatic experiences, and for anxiety and depression and the NEO-FFI Five Factor Personality Inventory. Forty-five of these participants responded to a postal questionnaire follow-up. In this survey the battery was repeated and also included a self-report diagnostic measure of post-traumatic stress disorder (PTSD).

RESULTS

The percentage of the sample meeting DSM-IV diagnostic criteria for PTSD at 6 weeks post-trauma was 30.8%. A small but significant relationship was found for negative attitudes to emotional expression at 1 week to predict intrusive symptoms and diagnosis at 6 weeks, over and above the independent relationships of initial symptoms, initial injury severity, personality and coping. The emotional expression measure was largely stable between the two points of measurement. More negative attitudes to emotional expression were related to less openness, extraversion and agreeableness personality domains.

CONCLUSIONS

Some support for the hypotheses was found in relation to the development of PTSD and for the status of attitudes to emotion as a stable trait related to personality factors. The potential importance of attitudes to emotional expression in therapy and other work is discussed.

Complete breast absence revisited

Congenital absence of the breast is a rare condition. The literature shows that there is much heterogeneity in its presentation as well as its inheritance. We described a mother and daughter with the condition and how the mother underwent breast reconstruction with use of bilateral transverse rectus abdominis myocutaneous flaps.

Decentring and distraction reduce overgeneral autobiographical memory in depression

BACKGROUND

Increased recall of categorical autobiographical memories is a phenomenon unique to depression and post-traumatic stress disorder, and is associated with a poor prognosis for depression. Although the elevated recall of categorical memories does not change on remission from depression, recent findings suggest that overgeneral memory may be reduced by cognitive interventions and maintained by rumination. This study tested whether cognitive manipulations could influence the recall of categorical memories in dysphoric participants.

METHODS

Forty-eight dysphoric and depressed participants were randomly allocated to rumination or distraction conditions. Before and after the manipulation, participants completed the Autobiographical Memory Test, a standard measure of overgeneral memory. Participants were then randomized to either a 'decentring' question (Socratic questions designed to facilitate viewing moods within a wider perspective) or a control question condition, before completing the Autobiographical Memory Test again.

RESULTS

Distraction produced significantly greater decreases in the proportion of memories retrieved that were categorical than rumination. Decentring questions produced significantly greater decreases in the proportion of memories retrieved that were categorical than control questions, with this effect independent of the prior manipulation.

CONCLUSIONS

Elevated categorical memory in depression is more modifiable than has been previously assumed; it may reflect the dynamic maintenance of a cognitive style that can be interrupted by brief cognitive interventions.

Resolving SNR 0540-6944 from LMC X-1 with Chandra

We examine the supernova remnant SNR 0540-697 in the Large Magellanic Cloud (LMC) using data from the Chandra Advanced CCD Imaging Spectrometer. The X-ray emission from this supernova remnant (SNR) had previously been hidden in the bright emission of the nearby X-ray binary LMC X-1; however, new observations with Chandra can finally reveal the SNR's structure and spectrum. We find the SNR to be a thick-shelled structure about 19 pc in diameter, with a brightened northeast region. Spectral results suggest a temperature of 0.31 keV and an X-ray luminosity (0.3-3.0 keV) of 8.4x1033 ergs s(-1). We estimate an age of 12,000-20,000 yr for this SNR, but note that this estimate does not take into account the possibility of cavity expansion or other environmental effects.

Observations on the covalent cross-linking of the binding domain (BD) of the high mobility group I/Y (HMG I/Y) proteins to DNA by FR66979

FR66979, a drug closely related to the mitomycin C class of antitumor antibiotics, is shown to covalently cross-link DNA to the DNA-binding domain of the High Mobility Group I/Y (HMG I/Y) DNA-binding proteins in the minor groove.

Synthesis of a netropsin conjugate of a water-soluble epi-quinocarcin analogue: the importance of stereochemistry at nitrogen

The efficient synthesis of a water-soluble C11a-epi-analogue (6b) of quinocarcin is described. This substance, and a netropsin amide conjugate (8) lack the capacity to inflict oxidative damage on DNA due to the stereoelectronic geometry of their oxazolidine nitrogen atoms. The capacity of these substances to alkylate DNA through the generation of an iminium species has been examined. Both compounds were found to be unreactive as DNA alkylating agents. The results of this study are discussed in the context of previous proposals on the mode of action of this family of antitumor alkaloids.

Kilohertz linewidth from frequency-stabilized mid-infrared quantum cascade lasers

Frequency stabilization of mid-IR quantum cascade (QC) lasers to the kilohertz level has been accomplished by use of electronic servo techniques. With this active feedback, an 8.5-microm QC distributed-feedback laser is locked to the side of a rovibrational resonance of nitrous oxide (N(2) O) at 1176.61cm (-1) . A stabilized frequency-noise spectral density of 42Hz/ radicalHz has been measured at 100 kHz; the calculated laser linewidth is 12 kHz.

Reductive Activation of a Hydroxylamine Hemiacetal Derivative of Dehydromonocrotaline: The First Reductively Activated Pyrrolizidine Alkaloid Capable of Cross-Linking DNA

The acute hepatotoxicity displayed by the pyrrolizidine alkaloids, which obviates their clinical utility, is a result of activation in vivo by cytochrome P450 mediated oxidation. Now the first reductively activated progenitor of the highly cytotoxic dehydropyrrolizidine alkaloid dehydromonocrotaline has been synthesized and demonstrated to mediate interstrand DNA cross-link formation (see scheme); pyrrolizidine alkaloids exert their cytotoxicity through the formation of DNA-DNA interstrand and DNA-protein cross-links.

Hair removal using an 810 nm gallium aluminum arsenide semiconductor diode laser: A preliminary study

BACKGROUND

Laser hair removal is a popular treatment method for removing unwanted hair. Several laser systems are available for laser hair removal. The gallium aluminum arsenide semiconductor diode (GAASD) laser is one of the newer laser modalities to be studied.

OBJECTIVE

To evaluate the efficacy of the GAASD laser system in removing unwanted hair.

METHODS

Twenty-six patients with brown or black hair growth were treated with the GAASD laser at fluences of 20-80 J/cm2. Hair regrowth was measured 4 weeks after the first treatment, 4 weeks after the second treatment, 4 weeks after the third treatment, and 4 weeks, 8 weeks, and 8 months after the fourth treatment.

CONCLUSION

GAASD laser treatment resulted in hair growth delay in all treated regions. Repeated laser treatments did not produce an increased number of vellus hairs. The percentage of hair reduction fluctuated between 5% and 13% with the second or third treatment averaging the highest percent reduction. In all cases, the percentage of hair reduction of the treatment sites evaluated at 8 months after the fourth treatment was less than both the second and third treatments (highest average percent reduction) and the fourth (last) treatment.

Effect of adrenocorticotrophic hormone on sodium appetite in mice

A main vector of the effects of stress is secretion of corticotrophin releasing factor (CRF), adrenocorticotrophin (ACTH), and adrenal steroids. Systemic administration of ACTH (2.8 microgram/day sc) for 7 days in BALB/c mice caused a very large increase of voluntary intake of 0.3 M NaCl equivalent to turnover of total body sodium content each day. Intracerebroventricular infusion of ACTH (20 ng/day) had no effect. Intracerebroventricular infusion of ovine CRF (10 ng/h for 7 days) caused an increase of sodium intake. The large sodium appetite-stimulating effect of systemic ACTH was not influenced by concurrent systemic infusion of captopril (2 mg/day). Induction of stress by immobilization of mice on a running wheel caused an increase in Na appetite associated with a 50% decrease of thymus weight, indicative of corticosteroid effects. The present data suggest that stress and the hormone cascade initiated by stress evoke a large sodium appetite in mice, which may be an important survival mechanism in environmental conditions causing stress.