A simple freeze dehydration method for studying epiphytic and epizoic communities using the scanning electron microscope

Freeze dehydration provides instant immobilisation and fixation of living materials to capture particular events and avoids the need for dehydration through an ethanol series for SEM viewing. Examples of the technique are given from freshwater epiphytic and epizoic communities. The species and community architectures found show the great need which exists for the study of the biology of these systems in their natural, undisrupted states.     

Influence of Sendai virus on carcinogenesis in strain A mice

An alkylating derivative of a hydrocarbon, 10-chloromethyl-9-chloroanthracene, gave rise to reduced numbers of chemically induced pulmonary adenomas in strain A mice enzootically infected with Sendai virus, while in the case of 7,12-dimethylbenz(a)anthracene, the opposite relationship was observed. Therefore, the presence or absence of viral infection was demonstrated to have a strong influence on carcinogenic susceptibility.     

Adrenocorticotropic hormone activation of adenylate cyclase in raphe neurons: Multiple regulatory pathways control serotonergic neuronal differentiation

The RN46A cell line was derived from embryonic day 13 rat medullary raphe cells by infection with a retrovirus encoding the temperature-sensitive mutant of SV 40 large T antigen (tsT-ag). The RN46A cell line is neuronally restricted and constitutively differentiates following a shift to nonpermissive temperature. Differentiated RN46A cells express low levels of tryptophan hydroxylase (TPH) but no detectable levels of serotonin (5-HT). Treatment of cultures with the adrenocorticotrophic hormone peptide ACTH_4–10 up-regulates the expression of TPH immunoreactivity in differentiated RN46A cells, but 5-HT synthesis requires initial treatment with ACTH_4–10, followed by partial membrane depolarizing conditions. Up-regulation of TPH by ACTH_4–10 is apparently due to activation of adenylate cyclase, whereas the increased 5-HT synthesis with membrane depolarization can be blocked with the voltage-sensitive Ca²⁺ -channel blockers nifedipine and ω-conotoxin. ACTH_4–10 treatment also markedly up-regulates the expression of the 5-HT reuptake transporter, as do dibutyryl cyclic AMP and forskolin; chronic membrane depolarization has no effect on 5-HT reuptake. The expression of the high-affinity 5-HT_1A receptor is increased threefold by ACTH_4–10 treatment during differentiation and fivefold by differentiation under partial membrane depolarizing conditions. Combining ACTH_4–10 treatment and membrane depolarization does not increase expression of the 5-HT_1A receptor further. 5-HT release is constitutive in ACTH-treated RN46A cells and linked to spontaneous synaptic vesicle fusion in RN46A cells. Considered with previous results, these data indicate that multiple effectors, ACTH, brain-derived neurotrophic factor, and membrane depolarization, have both distinct and overlapping effects that regulate specific elements of the serotonergic neuronal phenotype during differentiation and maturation. © 1995 John Wiley & Sons, Inc.     

Ca2+ sensitivity of BK channels in GH3 cells involves cytosolic phospholipase A2

To test thehypothesis that intracellular Ca²⁺activation of large-conductanceCa²⁺-activatedK⁺ (BK) channels involves thecytosolic form of phospholipase A₂ (cPLA₂), we first inhibited theexpression of cPLA₂ by treating GH₃ cells with antisenseoligonucleotides directed at the two possible translation start siteson cPLA₂. Western blot analysis and a biochemical assay of cPLA₂activity showed marked inhibition of the expression ofcPLA₂ in antisense-treated cells.We then examined the effects of intracellularCa²⁺ concentration([Ca²⁺]_i)on single BK channels from these cells. Open channel probability (P_o) for thecells exposed to cPLA₂ antisenseoligonucleotides in 0.1 µM intracellularCa²⁺ was significantly lower thanin untreated or sense oligonucleotide-treated cells, but the voltagesensitivity did not change (measured as the slope of theP_o-voltagerelationship). In fact, a 1,000-fold increase in[Ca²⁺]_ifrom 0.1 to 100 µM did not significantly increaseP_oin these cells, whereas BK channels from cells in the other treatmentgroups showed a normalP_o-[Ca²⁺]_iresponse. Finally, we examined the effect of exogenous arachidonic acidon theP_oof BK channels from antisense-treated cells. Although arachidonic aciddid significantly increaseP_o,it did so without restoring the[Ca²⁺]_isensitivity observed in untreated cells. We conclude that although [Ca²⁺]_idoes impart some basal activity to BK channels inGH₃ cells, the steepP_o-[Ca²⁺]_irelationship that is characteristic of these channels involves cPLA₂.

     

Resolving the Egg and Cholesterol Intake Controversy: New Clinical Insights Into Cholesterol Regulation by the Liver and Intestine

ObjectiveCardiovascular disease is the number one cause of death. Achieving American Heart Association low-density lipoprotein (LDL) cholesterol treatment goals is very difficult for many patients. The importance of a low cholesterol diet is controversial and not emphasized by most physicians. Of critical importance is determining whether each individual is a “hyper- or hypo-absorber” of dietary cholesterol. Furthermore, the quantity of each individual’s baseline daily dietary cholesterol and saturated fat intake is important in assessing the effect of added egg yolk cholesterol and saturated fat on blood LDL cholesterol.MethodsGut cholesterol is absorbed via a specific enteric receptor (the Niemann- Pick-like receptor). Dietary cholesterol contributes one fourth of the absorbed cholesterol, while the remaining gut cholesterol is derived from secreted bile cholesterol. This dietary quantity of cholesterol is significant when other determinants are constant. For some individuals, dietary cholesterol has no adverse effects and in others, a significant elevation in blood LDL cholesterol may occur.ResultsThere are no readily available blood tests to determine the effect of egg yolk cholesterol and saturated fat on an individual’s plasma LDL cholesterol. However, a one month trial of a low cholesterol and saturated fat diet will provide the needed information to make clinical decisions.ConclusionThis article delineates the mechanisms that are altered by genetic and environmental factors that determine the net effects of dietary cholesterol and saturated fat on circulating LDL cholesterol. It then makes a practical clinical recommendation based on these mechanisms.     

The revolving door of HIV care: Revising the service delivery cascade to achieve the UNAIDS 95-95-95 goals

Peter Ehrenkranz and co-authors present a cyclical cascade of care for people with HIV infection, aiming to facilitate assessment of outcomes.

Summary points

• Antiretroviral therapy (ART) for human immunodeficiency virus (HIV) prevents illness and death from HIV disease and transmission of HIV infection. To encourage global scale-up of ART, the Joint UN Program on HIV/AIDS (UNAIDS) issued the “95-95-95” targets for the HIV “cascade of care.” These targets state that by 2030, 95% of individuals living with HIV will know their HIV status, 95% of people with diagnosed HIV infection will receive ART, and 95% of those taking ART will have achieved suppression of the virus.
• While tremendous progress has been made toward achieving these targets, substantial gaps remain. The challenge of closing the final gaps requires reconsideration of the cascade itself.
• The 95-95-95 HIV care cascade depicts a linear and unidirectional continuum of care with one starting point (HIV diagnosis) and one ending point (treatment discontination or death). This simplification of the cascade oversimplifies the complex cycle of engagement, disengagement, temporary disuptions, reengagement, and transitions in care experienced by many people living with HIV (PLHIV).
• As the proportion of PLHIV who reinitiate ART after previously starting and stopping increases, we propose to update the HIV cascade of care to better reflect actual experiences of PLHIV. The new cascade makes the cycle of engaging and reengaging in HIV care both explicit and expected.
• The revised cascade will inform and prioritize efforts by communities, healthcare workers, implementers, program managers, policymakers, and donors to prevent missed clinic visits, overcome barriers to care reentry, and minimize onset of advanced HIV disease. It will also emphasize that morbidity, mortality, and onward transmission can be minimized by focusing interventions on anticipating, and then reducing, the duration of gaps in care.