Synthalin: a lost lesson for glucagon suppression in diabetes therapeutics

OBJECTIVES

Within mammalian pancreatic islets, there are two major endocrine cell types, beta-cells which secrete insulin and alpha-cells which secrete glucagon. Whereas, insulin acts to lower circulating glucose, glucagon counters this by increasing circulating glucose via the mobilisation of glycogen. Synthalin A (Syn A) was the subject of much research in the 1920s and 1930s as a potential pancreatic alpha-cell toxin to block glucagon secretion. However, with the discovery of insulin and its lifesaving use in patients with diabetes, research on Syn-A was discontinued.

KEY FINDINGS

This short review looks back on early studies performed with Syn A in animals and humans with diabetes. These are relevant today because both type 1 and type 2 diabetes are now recognised as states of not only insulin deficiency but also glucagon excess.

SUMMARY

Lessons learned from this largely forgotten portfolio of work and therapeutic strategy aimed at limiting the number or function of islet alpha-cells might be worthy of reconsideration.

The Genetic Links to Anxiety and Depression (GLAD) Study: Online recruitment into the largest recontactable study of depression and anxiety

BACKGROUND

Anxiety and depression are common, debilitating and costly. These disorders are influenced by multiple risk factors, from genes to psychological vulnerabilities and environmental stressors, but research is hampered by a lack of sufficiently large comprehensive studies. We are recruiting 40,000 individuals with lifetime depression or anxiety and broad assessment of risks to facilitate future research.

METHODS

The Genetic Links to Anxiety and Depression (GLAD) Study (www.gladstudy.org.uk) recruits individuals with depression or anxiety into the NIHR Mental Health BioResource. Participants invited to join the study (via media campaigns) provide demographic, environmental and genetic data, and consent for medical record linkage and recontact.

RESULTS

Online recruitment was effective; 42,531 participants consented and 27,776 completed the questionnaire by end of July 2019. Participants' questionnaire data identified very high rates of recurrent depression, severe anxiety, and comorbidity. Participants reported high rates of treatment receipt. The age profile of the sample is biased toward young adults, with higher recruitment of females and the more educated, especially at younger ages.

DISCUSSION

This paper describes the study methodology and descriptive data for GLAD, which represents a large, recontactable resource that will enable future research into risks, outcomes, and treatment for anxiety and depression.

A Comparison of Five Brief Screening Tools for HIV-Associated Neurocognitive Disorders in the USA and South Africa

Screening for HIV-associated neurocognitive disorders (HAND) is important to improve clinical outcomes. We compared the diagnostic sensitivity and specificity of the mini-mental state examination, International HIV dementia scale (IHDS), Montreal cognitive assessment, Simioni symptom questionnaire and cognitive assessment tool-rapid version (CAT-rapid) to a gold standard neuropsychological battery. Antiretroviral-experienced participants from Cape Town, South Africa, and Baltimore, USA, were recruited. The sensitivity and specificity of the five tools, as well as those of the combined IHDS and CAT-rapid, were established using 2 × 2 contingency tables and ROC analysis. More than a third (65165) had symptomatic HAND. In detecting HIV-D, the CAT-Rapid had good sensitivity (94 %) and weak specificity (52 %) (cut-point ≤10), while the IHDS showed fair sensitivity (68 %) and good specificity (86 %) (cut-point ≤10). The combined IHDS and CAT-rapid showed excellent sensitivity and specificity for HIV-D at a cut-off score of ≤16 (out of 20; 89 and 82 %). No tool was adequate in screening for any HAND. The combination IHDS and CAT-rapid tool appears to be a good screener for HIV-D but is only fairly sensitive and poorly specific in screening for any HAND. Screening for milder forms of HAND continues to be a clinical challenge.

Screen-detected breast cancer: does presence of minimal signs on prior mammograms predict staging or grading of cancer?

AIM

To investigate whether the presence of minimal signs on prior mammograms predict staging or grading of cancer.

MATERIALS AND METHODS

The previous mammograms of 148 consecutive patients with screen-detected breast cancer were examined. Women with an abnormality visible (minimal signs) on both current and prior mammograms formed the study group; the remaining patients formed the control group. Age, average size of tumour, tumour characteristic, histopathology, grade, and lymph node status were compared between the two groups, using Fisher's exact test. Cases in which earlier diagnosis would have made a significant prognostic difference were also evaluated.

RESULTS

Eighteen percent of patients showed an abnormality at the site of the tumour on previous mammograms. There was no statistically significant difference between the two groups with respect to age, average size of tumour, histopathology, grade or lymph node status with p-values being 0.609, 0.781, 0.938, and 0.444, respectively. The only statistically significant difference between the two groups was tumour characteristics with more microcalcifications associated with either mass or asymmetrical density seen in the study group (p=0.003). Five patients in the study group showed lymph node positivity and were grade 3, and therefore, may have had possible gain from earlier diagnosis.

CONCLUSION

The present study did not demonstrate a statistical difference in grading or staging between the group that showed "minimal signs" on prior mammograms versus normal prior mammograms. Microcalcification seems to be the most common characteristic seen in the missed cancer and a more aggressive management approach is suggested for breast microcalcifications.

Tel/PDGFRbeta induces stem cell differentiation via the Ras/ERK and STAT5 signaling pathways

OBJECTIVE

Fusion genes involving the platelet-derived growth factor receptor-beta (PDGFRbeta) are found in a subgroup of myeloproliferative neoplasms, with one such fusion, Tel/PDGFRbeta found in a subset of chronic myelomonocytic leukemia patients. Tel/PDGFRbeta results in constitutive activation of several signaling pathways and induces a myeloproliferative disease in mice, with signals via tyrosines 579/581 identified as being important for this phenotype. In this study, we have used a tetracycline-regulated system to express wild-type and the mutated F2 Tel/PDGFRbeta to identify the key signaling pathways, which drive Tel/PDGFRbeta-induced differentiation of embryonic stem (ES) cells.

MATERIALS AND METHODS

The leukemic oncogene Tel/PDGFRbeta and Tel/PDGFRbeta-F2 were inducibly expressed in ES cells and their effects on self-renewal, signal transduction, and gene expression patterns analyzed.

RESULTS

Tel/PDGFRbeta activated several major signal transduction pathways (signal transducers and activators of transcription [STAT] 3, STAT5, mitogen-activated protein kinases, phosphatidylinositol-3 kinase) in ES cells, but only specific inhibition of the mitogen-activated protein kinase kinase/extracellular regulated kinase (MEK/ERK) or STAT5 pathways was able to significantly prevent Tel/PDGFRbeta-induced differentiation and restore ES-cell self-renewal. Inhibiting the tyrosine kinase activity of the oncogene using Gleevec or PDGFRbeta inhibitor III also substantially prevented Tel/PDGFRbeta-induced differentiation and its ability to upregulate key genes involved in myelopoiesis. Tyrosines 579/581 played a critical role in mediating signals via the Ras/ERK and STAT5 pathways, with dual targeting of the tyrosine kinase activity of Tel/PDGFRbeta and the MEK/ERK pathway completely preventing Tel/PDGFRbeta-induced differentiation.

CONCLUSION

These findings suggest that targeted disruption of key signaling pathways in combination with the tyrosine kinase activity of leukemic oncogenes, such as Tel/PDGFRbeta, may result in more efficacious therapies for suppressing leukemic progression in the clinical setting.

Conformational switching and exciton interactions in hemicyanine-based bichromophores

Conformational changes in two hemicyanine-based bichromophores were demonstrated by varying the polarity as well as temperature of the medium. Dramatic changes in the ground and excited singlet state properties were observed upon folding of the bichromophores, due to the formation of intramolecular aggregates of H-type. These aspects were studied, in detail, using steady-state absorption and time-resolved fluorescence spectroscopy. Time-resolved fluorescence studies indicate that both the bichromophores exhibit a monoexponential decay, with a short lifetime, in mixed toluene-CH(2)Cl(2) solvents having lower proportions of toluene. Interestingly, biexponential decay with short and long-lived species was observed at higher proportions of toluene, due to the presence of unfolded and folded forms. Folding results in the intramolecular stacking of the chromophores which restrict their torsional dynamics, leading to a longer lifetime. Upon laser excitation, the folded form of the bichromophore undergoes rapid conformational changes, due to photoinduced thermal dissociation.

Biradical intermediates in the photoisomerization of dibenzodihydropentalenofurans to dibenzosemibullvalenes

The photoisomerization of a few substituted dibenzodihydropentalenofurans to the corresponding dibenzosemibullvalenes is reported. Steady-state photolysis of the dibenzodihydropentalenofurans 3a--d gave the corresponding dibenzosemibullvalenes 2a--d in nearly quantitative yields. The quantum yields of this photoisomerization were found to be in the range 0.17--0.26. Laser flash photolysis studies of the dibenzodihydropentalenofurans 3a-e showed transients, with absorption maxima around 410 nm and decaying by first-order kinetics. The lifetimes were in the range 14--30 micros in degassed benzene at 25 degrees C. These transients were readily quenched (trapped) by molecular oxygen, and the Stern-Völmer quenching constants were found to be in the range (2.45--3.17) x 10(9) M(-1) s(-1). As a representative example, the 1,3-biradical intermediate from 3e was trapped by molecular oxygen to give the corresponding endoperoxide 11e. The transients were weakly quenched by triplet/radical quenchers such as 2,2,6,6-tetramethylpiperinyl-1-oxy (TEMPO) and 4-hydroxy-2,2,6,6-tetramethylpiperinyl-1-oxy (HTEMPO), and the quenching constants are found to be in the range (1.09--3.19) x 10(6) M(-1) s(-1). The decay rates of the transients were found to be temperature dependent and obeyed the Arrhenius equation. For example, the activation energy of the transient from 3a was approximately 4.5 kcal mol(-1) and the Arrhenius preexponential factor log(A/s(-1)) for the decay of the transients was approximately 7.5. On the basis of our studies, these transients were assigned as the ground-state triplet biradicals, generated by the cleavage of the C--O bond of the starting dibenzodihydropentalenofurans.

Place learning in virtual space. III: Investigation of spatial navigation training procedures and their application to fMRI and clinical neuropsychology

This paper describes the utilization of a desktop virtual environment task, the Computer-Generated (C-G) Arena, in the study of human spatial navigation. First, four experiments examined the efficacy of various training procedures in the C-G Arena. In Experiment 1, participants efficiently located a hidden target after only observing the virtual environment from a fixed position (placement learning). In Experiment 2, participants efficiently located a hidden target after only observing an experimenter search the virtual environment (observational learning). In Experiment 3, participants failed to display a latent learning effect in the virtual environment. In Experiment 4, all training procedures effectively taught participants the layout of the virtual environment, but the observational learning procedure most effectively taught participants the location of a hidden target within the environment. Finally, two experiments demonstrated the application of C-G Arena procedures to neuroimaging (Experiment 5) and neuropsychological (Experiment 6) investigations of human spatial navigation.

Nanostructured thin films of C60-aniline dyad clusters: electrodeposition, charge separation, and photoelectrochemistry

Clusters of C60-aniline dyads are deposited as thin films on nanostructured SnO2 electrodes under the influence of an electric field. At low applied DC voltage (<5 V) the clusters in toluene/acetonitrile (1:3) mixed solvent grow in size (from 160 nm to approximately 200 nm in diameter) while at higher voltages (>50 V) they are deposited on the electrode surface as thin films. The C60- aniline dyad cluster films when cast on nanostructured SnO2 films are photoelectrochemically active and generate photocurrent under visible light excitation. These nanostructured fullerene films are capable of delivering relatively large photocurrents (up to approximately 0.2 mA cm(-2), photoconversion efficiency of 3-4%) when employed as photoanodes in photoelectrochemical cells. Both luminescence and transient absorption studies confirm the formation of charge transfer product (C60 anion) following UV/Vis excitation of these films. Photo-induced charge separation in these dyad clusters is followed by the electron injection from C60-anion moiety into the SnO2 nanocrystallites. The oxidized counterpart is reduced by the redox couple present in the electrolyte, thus regenerating the dyad clusters. The feasibility of casting high surface area thin fullerene films on electrode surfaces has opened up new avenues to utilize dyad molecules of sensitizer bridge donor type in light energy conversion devices, such as solar cells.

Humans with traumatic brain injuries show place-learning deficits in computer-generated virtual space

Spatial learning and memory has been linked to the hippocampus and temporal lobes and though these areas are often damaged in traumatic brain injury (TBI), spatial learning deficits after TBI have not received much attention. In the present study, a virtual environment was used to challenge people with TBI to solve a task comparable to the Morris water maze, which in turn has been shown to be highly sensitive to hippocampal and frontal lobe dysfunction in laboratory animals. A regular computer monitor was used to present 12 participants with TBI and 12 age- and sex-matched comparison participants with a computer-generated, three-dimensional "virtual arena maze," consisting of a large round arena within a very large square room. Participants were required to learn the place of an invisible target on the floor of the room based solely on distal cues on the walls of the room. Eight of the 12 participants with moderate to severe TBI showed substantial place-learning deficits in comparison to the uninjured participants. Performance in the virtual environment correlated with self-reported frequency of wayfinding problems in everyday life and with scores on a test of episodic memory, the Rivermead Behavioural Memory Task. These data confirm that deficits in spatial learning and memory follow TBI, and suggest that the virtual arena maze may provide a new method for objectively assessing them.

The effects of growth factors associated with osteoblasts on prostate carcinoma proliferation and chemotaxis: implications for the development of metastatic disease

The extensive mortality and morbidity associated with prostate cancer is caused by the high prevalence of metastatic disease at the time of diagnosis. The area most frequently involved in metastatic prostate cancer is the skeleton. Unlike other cancers, which metastasize to bone and destroy the bone matrix, prostate cancer is unique in that it is osteogenic, resulting in the formation of dense, sclerotic bone with high levels of osteoblastic activity. We proposed that factors produced by bone cells may be responsible for the development of prostate carcinoma metastasis. We studied the effects of these growth factors on prostate cell proliferation by [3H]thymidine incorporation and chemotaxis by the double-filter chamber method. Three prostate carcinoma cell lines were studied, LNCaP (androgen responsive) and PC-3 and DU-145 (androgen unresponsive). The bone-associated growth factors tested were: insulin-like growth factors I and II (IGF-I, IGF-II), transforming growth factor beta, interleukin (IL)-1 beta, IL-6, and tumor necrosis factor alpha (TNF-alpha), IGF-I and IGF-II significantly increased proliferation in all three cell lines, whereas IL-6, TNF-alpha, and IL-1 beta significantly decreased proliferation. Transforming growth factor beta induced a biphasic response in proliferation in DU-145 and PC-3 cells and produced no response on LNCaP cells. Increased cell chemotaxis occurred in the presence of IGF-I and IGF-II, and decreased cell chemotaxis occurred with the addition of TNF-alpha and IL-1 beta. These data indicate that growth factors produced by bone cells alter prostate carcinoma cell proliferation and chemotaxis and suggest that modulations of the production of these factors may be a potential therapeutic intervention in deterring the metastasis of prostate carcinoma to bone.

Effects of the calciotrophic peptides calcitonin and parathyroid hormone on prostate cancer growth and chemotaxis

BACKGROUND

The most common site of metastases in prostate cancer is the skeleton and occurs in 70-80% of patients with prostate carcinoma. Calciotrophic peptides are important in the growth and development of normal bone matrix.

METHODS

Three human prostate carcinoma cells lines, DU-145, PC-3, and LNCaP, were exposed to varying concentrations of parathyroid hormone (PTH) or calcitonin (CT). Cell proliferation and chemotaxis were assessed.

RESULTS

Proliferation increased in LNCaP cells in a dose-dependent manner following treatment with PTH. Proliferation was not altered in PC-3 cells in response to PTH. Proliferation was decreased in DU-145 and PC-3 cells and increased in LNCaP cells after treatment with CT. Cell chemotaxis was increased in the presence of PTH in DU-145 and PC-3 cells compared to vehicle-treated controls.

CONCLUSIONS

The combined proliferation and chemotaxis data suggest that PTH has a dual role in prostate carcinoma resulting in an increase in the number and migration of selected prostate cancer cells. With CT, chemotaxis was unchanged in the DU-145 and PC-3 cells and significantly elevated in the LNCaP cell line. The calciotrophic hormones, PTH and CT, may play an integral role in the regulation of prostate cell growth and metastases.

Transrectal ultrasound appearances of granulomatous prostatitis

Granulomatous prostatitis is an unusual, but well-recognized entity frequently mistaken for carcinoma on both digital rectal examination and transrectal ultrasound. The ultrasonographic findings of 11 patients with histologically-proven granulomatous prostatitis are reviewed.

Case report: the vanishing ring sign--an unusual CT manifestation of multiple sclerosis

Ring-like computed tomographic (CT) enhancement of a solitary cerebral mass usually indicates neoplasm or abscess. A 64-year-old man with this sign was found to have multiple sclerosis (MS), and following oral steroid treatment, it disappeared.