Impaired Expression of Humanin during Adrenocortical Carcinoma

The discovery of mitochondria-derived peptides (MDPs) has provided a new perspective on mitochondrial function. MDPs encoded by mitochondrial DNA (mtDNA) can act as hormone-like peptides, influencing cell survival and proliferation. Among these peptides, humanin has been identified as a crucial factor for maintaining cell survival and preventing cell death under various conditions. Adrenocortical carcinoma (ACC) is a rare and aggressive malignancy that results from adrenal hormone dysfunction. This study aimed to investigate humanin expression in the adrenal tissue and serum of patients with ACC. For the first time, our study revealed significant reduction in the mRNA expression of humanin in patients with ACC compared to healthy controls. However, no significant changes were observed in the serum humanin levels. Interestingly, we identified a positive correlation between patient age and serum humanin levels and a negative correlation between tumor size and LDL levels. While the impaired expression of humanin in patients with ACC may be attributed to mitochondrial dysfunction, an alternative explanation could be related to diminished mitochondrial copy number. Further investigations are warranted to elucidate the intricate relationship among humanin, mitochondrial function, and ACC pathology.

Inferring mechanical properties of the SARS-CoV-2 virus particle with nano-indentation tests and numerical simulations

The pandemic caused by the SARS-CoV-2 virus has claimed more than 6.5 million lives worldwide. This global challenge has led to accelerated development of highly effective vaccines tied to their ability to elicit a sustained immune response. While numerous studies have focused primarily on the spike (S) protein, less is known about the interior of the virus. Here we propose a methodology that combines several experimental and simulation techniques to elucidate the internal structure and mechanical properties of the SARS-CoV-2 virus. The mechanical response of the virus was analyzed by nanoindentation tests using a novel flat indenter and evaluated in comparison to a conventional sharp tip indentation. The elastic properties of the viral membrane were estimated by analytical solutions, molecular dynamics (MD) simulations on a membrane patch and by a 3D Finite Element (FE)-beam model of the virion's spike protein and membrane molecular structure. The FE-based inverse engineering approach provided a reasonable reproduction of the mechanical response of the virus from the sharp tip indentation and was successfully verified against the flat tip indentation results. The elastic modulus of the viral membrane was estimated in the range of 7-20 MPa. MD simulations showed that the presence of proteins significantly reduces the fracture strength of the membrane patch. However, FE simulations revealed an overall high fracture strength of the virus, with a mechanical behavior similar to the highly ductile behavior of engineering metallic materials. The failure mechanics of the membrane during sharp tip indentation includes progressive damage combined with localized collapse of the membrane due to severe bending. Furthermore, the results support the hypothesis of a close association of the long membrane proteins (M) with membrane-bound hexagonally packed ribonucleoproteins (RNPs). Beyond improved understanding of coronavirus structure, the present findings offer a knowledge base for the development of novel prevention and treatment methods that are independent of the immune system.

The Enhanced Expression of ZWILCH Predicts Poor Survival of Adrenocortical Carcinoma Patients

Zwilch kinetochore protein (ZWILCH) plays a key role in proper cell proliferation. The upregulation of the ZWILCH gene was observed in many types of cancers, but the association of ZWILCH with adrenocortical carcinoma (ACC) was not investigated so far. The main aim of the presented study was to verify if the enhanced level of the ZWILCH gene can be used as a diagnostic marker for ACC development and progression, as well as a predictor of survival time for ACC patients. The performed analyses included investigation of the ZWILCH expression profile in tumors with publicly available TCGA (The Cancer Genome Atlas) datasets and transcriptomic data from the Gene Expression Omnibus (GEO) database, as well as, in human biological samples of normal adrenal, adrenocortical carcinoma and in commercially available tissue microarrays. The findings demonstrate statistically significant higher ZWILCH gene expression in ACC tissue in comparison with normal adrenal glands. Furthermore, there is a strong correlation between ZWILCH upregulation and tumor mitotic rate and the probability of patient survival. The enhanced ZWILCH level is also connected with the activation of genes involved in cell proliferation and the inhibition of genes related to the immune system. This work contributes to a better understanding of the role of ZWILCH as an ACC biomarker and diagnostic tool.

Finite element modeling of alpha-helices and tropocollagen molecules with reference to the spike of SARS-CoV-2

The newly developed finite element modeling at the atomic scale was used to predict the static and dynamic response of the alpha-helix (AH) and tropocollagen (TC) protein fragments, the main building blocks of the spike of the SARS-CoV-2. The geometry and morphology of the spike's stalk and its connection to the viral envelope were determined from the combination of most recent Molecular Dynamics simulation and images of Cryo-Electron microscope. The stiffness parameters of the covalent bonds in the main chain of the helix were taken from the literature. The AH and TC were modeled using both beam elements (wire model) and shell elements (ribbon model) in finite element analysis to predict their mechanical properties under tension. The asymptotic stiffening features of AH and TC under tensile loading were revealed and compared with a new analytical solution. The mechanical stiffnesses under other loading conditions, including compression, torsion and bending were also predicted numerically and correlated with the results of the existing MD simulations and tests. The mode shapes and natural frequencies of the spike were predicted using the built FE model. The frequencies were shown to be within the safe range of 1-20 MHz routinely used for medical imaging and diagnosis by means of ultrasound. These results provide a solid theoretical basis for using ultrasound to study damaging coronavirus through transient and resonant vibration at large deformations.

Biological response of adrenal carcinoma and melanoma cells to mitotane treatment

A previous case report described an adrenal incidentaloma initially misdiagnosed as adrenocortical carcinoma (ACC), which was treated with mitotane. The final diagnosis was metastatic melanoma of unknown primary origin. However, the patient developed rapid disease progression after mitotane withdrawal, suggesting a protective role for mitotane in a non-adrenal-derived tumor. The aim of the present study was to determine the biological response of primary melanoma cells obtained from that patient, and that of other established melanoma and ACC cell lines, to mitotane treatment using a proliferation assay, flow cytometry, quantitative PCR and microarrays. Although mitotane inhibited the proliferation of both ACC and melanoma cells, its role in melanoma treatment appears to be limited. Flow cytometry analysis and transcriptomic studies indicated that the ACC cell line was highly responsive to mitotane treatment, while the primary melanoma cells showed a moderate response in vitro. Mitotane modified the activity of several key biological processes, including ‘mitotic nuclear division’, ‘DNA repair’, ‘angiogenesis’ and ‘negative regulation of ERK1 and ERK2 cascade’. Mitotane administration led to elevated levels of DNA double-strand breaks, necrosis and apoptosis. The present study provides a comprehensive insight into the biological response of mitotane-treated cells at the molecular level. Notably, the present findings offer new knowledge on the effects of mitotane on ACC and melanoma cells.

Effect of receptors on the resonant and transient harmonic vibrations of Coronavirus

The paper is concerned with the vibration characteristics of the Coronavirus family. There are some 25-100 receptors, commonly called spikes protruding from the envelope shell of the virus. Spikes, resembling the shape of a hot air balloon, may have a total mass similar to the mass of the lipid bi-layer shell. The lipid proteins of the virus are treated as homogeneous elastic material and the problem is formulated as the interaction of thin elastic shell with discrete masses, modeled as short conical cross-sectional beams. The system is subjected to ultrasonic excitation. Using the methods of structural acoustics, it is shown that the scattered pressure is very small and the pressure on the viral shell is simply the incident pressure. The modal analysis is performed for a bare shell, a single spike, and the spike-decorated shell. The predicted vibration frequencies and modes are shown to compare well with the newly derived closed-form solutions for a single spike and existing analytical solutions for thin shells. The fully nonlinear dynamic simulation of the transient response revealed the true character of the complex interaction between local vibration of spikes and global vibration of the multi-degree-of-freedom system. It was shown that harmonic vibration at or below the lowest resonant modes can excite large amplitude vibration of spikes. The associated maximum principal strain in a spike can reach large values in a fraction of a millisecond. Implications for possible tearing off spikes from the shell are discussed. Another important result is that after a finite number of cycles, the shell buckles and collapses, developing internal contacts and folds with large curvatures and strains exceeding 10%. For the geometry and elastic properties of the SARS-CoV-2 virus, these effects are present in the range of frequencies close to the ones used for medical ultrasound diagnostics.

Adropin Stimulates Proliferation and Inhibits Adrenocortical Steroidogenesis in the Human Adrenal Carcinoma (HAC15) Cell Line

Adropin is a multifunctional peptide hormone encoded by the ENHO (energy homeostasis associated) gene. It plays a role in mechanisms related to increased adiposity, insulin resistance, as well as glucose, and lipid metabolism. The low adropin levels are strongly associated with obesity independent insulin resistance. On the other hand, overexpression or exogenous administration of adropin improves glucose homeostasis. The multidirectional, adropin-related effects associated with the regulation of metabolism in humans also appear to be attributable to the effects of this peptide on the activity of various elements of the endocrine system including adrenal cortex. Therefore, the main purpose of the present study was to investigate the effect of adropin on proliferation and secretory activity in the human HAC15 adrenal carcinoma cell line. In this study, we obtained several highly interesting findings. First, GPR19, the main candidate sensitizer of adrenocortical cells to adropin, was expressed in HAC15 cells. Moreover, GPR19 expression was relatively stable and not regulated by ACTH, forskolin, or adropin itself. Our findings also suggest that adropin has the capacity to decrease expression levels of steroidogenic genes such as steroidogenic acute regulatory protein (StAR) and CYP11A1, which then led to a statistically significant inhibition in cortisol and aldosterone biosynthesis and secretion. Based on whole transcriptome study and research involving transforming growth factor (TGF)-β type I receptor kinase inhibitor we demonstrated that attenuation of steroidogenesis caused by adropin is mediated by the TGF-β signaling pathway likely to act through transactivation mechanism. We found that HAC15 cells treated with adropin presented significantly higher proliferation levels than untreated cells. Using specific intracellular inhibitors, we showed that adropin stimulate proliferation via ERK1/2 and AKT dependent signaling pathways. We have also demonstrated that expression of GPR19 is elevated in adrenocortical carcinoma in relation to normal adrenal glands. High level of GPR19 expression in adrenocortical carcinoma may constitute a negative prognostic factor of disease progression.

Effect of working environment and procedural strategies on mechanical performance of bioresorbable vascular scaffolds

Polymeric bioresorbable scaffolds (BRS), at their early stages of invention, were considered as a promising revolution in interventional cardiology. However, they failed dramatically compared to metal stents showing substantially higher incidence of device failure and clinical events, especially thrombosis. One problem is that use of paradigms inherited from metal stents ignores dependency of polymer material properties on working environment and manufacturing/deployment steps. Unlike metals, polymeric material characterization experiments cannot be considered identical under dry and submerged conditions at varying rates of operation. We demonstrated different material behaviors associated with variable testing environment and parameters. We, then, have employed extracted material models, which are verified by computational methods, to assess the performance of a full-scale BRS in different working condition and under varying procedural strategies. Our results confirm the accepted notion that slower rate of crimping and inflation can potentially reduce stress concentrations and thus reduce localized damages. However, we reveal that using a universal set of material properties derived from a benchtop experiment conducted regardless of working environment and procedural variability may lead to a significant error in estimation of stress-induced damages and overestimation of benefits procedural updates might offer. We conclude that, for polymeric devices, microstructural damages and localized loss of structural integrity should complement former macroscopic performance-assessment measures (fracture and recoil). Though, to precisely capture localized stress concentration and microstructural damages, context-related testing environment and clinically-relevant procedural scenarios should be devised in preliminary experiments of polymeric resorbable devices to enhance their efficacy and avoid unpredicted clinical events. STATEMENT OF SIGNIFICANCE: Bioresorbable scaffolds (BRS) with the hope to become the next cardiovascular interventional revolution failed in comparison to metal stents. When BRS were characterized using methods for metal stents, designers were misled to seek problem sources at erroneous timeframe and use inefficient indicators, and thus no signal of concern emerged. We demonstrated fundamental flaws associated with applying a universal set of material properties to study device performances in different phases of manufacturing/implantation, and these may be responsible for failure in predicting performance in first-generation BRS. We introduced new criterion for the assessment of structural integrity and device efficacy in next-generation BRS, and indeed all devices using polymeric materials which evolve with the environment they reside in.

Modelling of cracks developed in lithium-ion cells under mechanical loading

This research reports on an experimental and numerical study of material failure in the electrode assemblies (i.e. “jelly roll” and/or “electrode stack”) of lithium-ion batteries after local mechanical loading.

Alternative 3' acceptor site in the exon 2 of human PAX8 gene resulting in the expression of unknown mRNA variant found in thyroid hemiagenesis and some types of cancers

PAX8 gene encodes one of the transcription factors engaged in the regulation of proper development of thyroid gland as well as Müllerian and renal/upper urinary tracts. So far, six alternatively spliced transcripts were reported, however, sequences of only four were deposited in the NCBI database. Here, we evaluate a fragment of a novel variant of PAX8 mRNA formed by an alternative 3' acceptor site located in the second exon. The molecular outcome encompasses extension of the 5' untranslated region of exon two by 97 nucleotides as is evident from mRNA. This new insert may impair binding of mRNA to the ribosome and in consequence significantly decrease expression of the PAX8 protein. Here, we show for the first time that the novel insert in exon two might be associated with congenital thyroid hemiagenesis and influence development of different types of cancer.

Alternative 3' acceptor site in the exon 2 of human PAX8 gene resulting in the expression of unknown mRNA variant found in thyroid hemiagenesis and some types of cancers

PAX8 gene encodes one of the transcription factors engaged in the regulation of proper development of thyroid gland as well as Müllerian and renal/upper urinary tracts. So far, six alternatively spliced transcripts were reported, however, sequences of only four were deposited in the NCBI database. Here, we evaluate a fragment of a novel variant of PAX8 mRNA formed by an alternative 3' acceptor site located in the second exon. The molecular outcome encompasses extension of the 5' untranslated region of exon two by 97 nucleotides as is evident from mRNA. This new insert may impair binding of mRNA to the ribosome and in consequence significantly decrease expression of the PAX8 protein. Here, we show for the first time that the novel insert in exon two might be associated with congenital thyroid hemiagenesis and influence development of different types of cancer.

Determination of vanadium species in environmental samples

The distribution of vanadium between different oxidation states plays an important role in its environmental chemistry. As its two most commons forms, vanadium(IV) and vanadium(V) have different toxicity, speciation analysis of this element is necessary for environmental and biological samples. This paper presents recent research on the determination of vanadium species. Some important problems concerning stability of vanadium forms and proposed separation techniques are discussed.

Massive bleeeding from upper gastrointestinal tract as a symptom of rupture of splenic artery aneurysm to stomach

Background

Splenic artery aneurysm is the most common aneurysm of visceral vessels. Their rupture usually leads to massive bleeding, being a direct life threat. Splenic artery aneurysms usually rupture into the free peritoneal cavity, and much less frequently into the lumen of the gastrointestinal tract.

Case Report

We describe the case of a 38-year-old male patient, who, as a result of chronic pancreatitis, developed a false aneurysm of the splenic artery, which initially caused necrosis of the large intestine and bleeding into its lumen, and subsequently necrosis of the posterior stomach wall with the aneurysm rupture to the stomach lumen with a dramatic course.

Conclusions

The case described confirms that splenic artery aneurysm can be a cause of bleeding to both upper and lower parts of the gastrointestinal tract, and the aneurysm rupture is usually of a dramatic and life-threatening course.

Sorption Behavior of Vanadium on Silica Gel Modified with Tetrakis(4-carboxyphenyl)porphyrin

Tetrakis(4-carboxyphenyl)porphyrin (TCPP) has been loaded on aminopropyl-silica gel by physical adsorption and by direct immobilization through formation of an amide bond to obtain chelating sorbents. These sorbents have been studied for preconcentration and separation of vanadium prior to its determination by atomic absorption spectrometry. Several parameters, such as sorption capacity of the chelating resin, pH for retention of V(IV) and V(V), volume of sample and eluent, were evaluated. Both vanadium species sorbed on TCPP-modified resin could be eluted using 2 mol L(-1) nitric acid solution. The recovery values were > 94% and preconcentration factor of 160 was obtained. For speciation analysis, cyclohexane-1,2-diaminetetraacetic acid (CDTA) was added to the sample for complexation of vanadium(IV), which was not retained on the microcolumn. The proposed method was examined for reference standard materials (TM-25.2 and CAAS-3) as well as for river water samples.

[Gastro-oesophageal reflux disease presenting as laryngeal pathology--epidemiology, symptoms, diagnosis. Preliminary report]

Symptoms from the ears, throat, nose and larynx--the laryngeal mask's manifestations of gastroesophageal reflux disease (GERD) are important clinical problem of significant occurrence.

AIM

(1) Determination of GERD's frequency of occurrence, especially within the group of patients with the pathology of the posterior laryngeal commissure. (2) Evaluation of the effective algorithms for detecting and management of patients demonstrating symptoms of laryngeal mask, which develop on the ground of gastroesophageal reflux disease. The investigation included 9 patients who were hospitalized in the Department of Otolaryngology of Karol Marcinkowski University of Medical Sciences in Poznań. Every patient was carefully interviewed by means of 3 questionnaires: the first one being Karlsson's general questionnaire, the second one--author's questionnaire designed in the Department of Otolaryngology of Medical Academy in Poznań which emphasises laryngeal symptoms; and the third one being the inquiry including serious past diseases, regularly taken medications, and stimulants. The objective condition of the hypopharynx and larynx was estimated on the basis of indirect laryngoscopy, followed by manometric examination of the oesophagus and 24-hour pH-metry carried out in Motility Laboratory of Surgical Department. 8 patients (88.9%) out of 9 were diagnosed as having GERD on the ground of the questionnaires as well as on the base of the results from the 24-hour pH-metry, and among 7 patients (87.5%) out of the 8 motility disfunction of the oesophagus was detected. Within the group of 8 patients with diagnosed GERD on the ground of additional tests 3 patients (37.5%) were diagnosed as having posterior laryngitis, 2 patients (25%) were diagnosed as having chronic laryngitis and the last 1 (12.5%) suffering from dysphagia. Among 3 patients (37.5%) with tumors of the larynx of rare location within the posterior laryngeal commissure coexistence of gastroesophageal reflux disease (GERD) was proved. The remaining 1 patient (11.1%) with the larynx cancer had no confirmation of GERD. The connection between chronic laryngitis and gastroesophageal reflux disease and/or motility disfunction of the oesophagus described in the literature was confirmed within the group of examined patients. Awareness of GERD and diagnostics carried out in that direction is needed in the group of patients with typical symptoms of the laryngeal mask. Significant frequency of coexistence of gastroesophageal reflux disease and pathology of the posterior laryngeal commissure requires effective algorithms for management of these patients.

Flow-injection sample preconcentration for ion-pair chromatography of trace metals in waters

Selected trace transition metal ions have been determined in an FIA/HPLC hyphenated system using on-line preconcentration on cellulose functionalised sorbent Cellex P. For HPLC separation ion-pair chromatography was employed with spectrophotometric detection at 510 nm using post-column derivatisation with PAR. Favourable kinetic conditions of sorption and elution as well as optimisation of hyphenated system allowed to obtain detection limits at sub-microgL(-1) level at 25 min preconcentration time. The developed method was employed for determination of Co(II), Ni(II), Cd(II) and Mn(II) in river water with reasonable agreement of obtained results with electrothermal AAS determination.

Early dietary experience influences ontogeny of intestine in response to dietary lipid changes in later life

This study was undertaken to test the hypothesis that a change in the mother's diet at the time of birth and continued during suckling modifies the intestinal transport of nutrients in the suckling offspring. Pregnant rat dams were fed one of four semisynthetic diets during pregnancy [high or low n-6/n-3 diet or a diet enriched with arachidonic acid (AA) or docosahexaenoic acid (DHA)] and were fed the same diet at the time of birth or switched to another diet. The greatest body weight gain was in the suckling rats (15-16 days of age) fed a low n-6/n-3 diet. Switching from this diet caused weight loss, and the observed weight gain with the low n-6/n-3 diet was prevented by previous exposure of the mother to the high n-6/n-3 diet or the AA- or DHA-containing diet. Although continuous feeding of a high n-6/n-3 diet to the mother during pregnancy and lactation was associated with the lowest in vitro rates of fructose uptake, switching the mother to another diet during lactation did not necessarily correct the low absorption. In contrast, continuous feeding of a high n-6/n-3 diet to the mother during pregnancy and lactation is associated with the highest maximal transport rate of glucose uptake into the jejunum and ileum. Jejunal uptake of fatty acids 12:0, 18:0, 18:3(n-3), and cholesterol was less with the low n-6/n-3 diet compared with the high n-6/n-3 diet, whereas the ileal uptake of 18:0 and 18:3(n-3) was higher with the low n-6/n-3 diet. Thus the ontogeny of the intestine is critically influenced by the mother's diet during gestation as well as during the nursing period. Some of the diet-associated changes in nutrient uptake resulting from the mother's diet during pregnancy could be corrected by dietary interventions introduced after birth.

[45 years of experience in surgical treatment for cancer of the large intestine]

The aim of the study was to evaluate the results of surgical treatment of colorectal cancer during 45 years of existence of the Department. In this time 1478 cases of rectal cancer and 1008 cases of colon cancer were operated on. Most commonly the diseases occurred between the sixth and seventh decade of live (32.8%). Histology revealed tubular adenocarcinoma in 83.3% of the cases, mucinous adenocarcinoma in 13.5% and other types in 3.2%. The choice of the surgical procedure was based on the individual characteristics of each case, including: localisation of the tumor, histological type, clinical staging, sex of the patient, obesity and overall operative risk. The tumor was localised less then 10 cm above the anal verge in 70% of the patients with rectal cancer. Well differentiated carcinomas (G1) were seen in 32% of the patients, moderately differentiated carcinomas (G2) in 57% and poorly differentiated (G3) in 11%. Curative resections were performed in 64.7% of the patients (1608 cases) and palliative procedures in 35.3% of the patients (878 cases). The mortality rate after curative surgery was 6% and after palliative procedures 5%. The use of combined therapy consisting of surgical treatment and chemo- or radiotherapy allowed for obtaining five years survival rate of 57.4%, local recurrences were seen in 21% of patients. Analysing our own material we evaluated the radicality of different types of operations and the possibility of preserving the sphincter apparatus.

[Combined treatment of large bowel cancer]

During the years 1989 to 1994, in the Department of General Surgery we performed surgery on 800 cases of large bowel cancer. The cases comprised 412 men (51.5%) and 388 women (48.5%), aged 25 to 85, the most numerous age group ranging from 50 to 70 (60%). Radical surgery was carried out on 501 cases (62.7%) and palliative surgery on 299 cases (37.3%). In cases with histopathological evaluation pTNM-T1N0M0 or T2N0M0 we refrained from chemo- and radiotherapy. In cases of rectal cancer with advanced staging T3N1M0 or T4N2M1 we applied radiotherapy, whereas in cases of cancer localized on other parts of large bowel we had recourse to chemotherapy as combined treatment. Radiotherapy was applied irrespective of grading, whereas chemotherapy was applied in cases of cancer with grading G2 and G3. Radiative energy was used in 65 cases and chemotherapy in 120 cases. Postoperational mortality amounted to 6%. Five years survival after radical surgery achieved 57.4%. Local recurrence took place in 21% of the cases. The control group consisted of the cases subjected to surgery in the years 1984-1989 when only surgery was performed and 5-years survival after radical surgery amounted to 48% and local recurrence was found in 30% of the cases.

Influence of genotype on diet-induced changes in membrane phosphatidylcholine and phosphatidylethanolamine composition of splenocytes, liver nuclear envelope and liver mitochondria

Inbred congenic mice of strains MRL/Mp-lpr/lpr (lpr/lpr) and MRL/Mp(-)+/+ (+/+) were fed nutritionally adequate semipurified diets containing 20% (w/w) fat and differing in linoleic acid content. Levels of linoleic acid (18:2n-6) and arachidonic acid (20:4n-6) in phospholipids of splenocytes, liver mitochondria and liver nuclear envelopes were determined. Membranes of lpr/lpr mice exhibited significantly lower levels of 18:2n-6 and 20:4n-6 in phospholipids compared with the +/+ strain. The high linoleic acid diet increased incorporation of 18:2n-6 and 20:4n-6 in most phospholipid fractions of these membranes. These observations indicate that genotype as well as dietary 18:2n-6 content significantly influenced incorporation of 18:2n-6 and 20:4n-6 into membrane phospholipids. The results also suggest that membrane compositional abnormalities found in the lpr/lpr mice, which develop lymphoma and age faster than +/+ mice, are not restricted to the immune system but also extend to other organs. Differences observed in phospholipid fatty acid composition in splenocytes and liver subcellular membranes for mice fed diets differing in linoleic acid content suggest that the early expression of the lpr gene resulting in progression of autoimmunity may be delayed through dietary manipulation.

The relationship between retinal vessel tortuosity, diameter, and transmural pressure

Increases in retinal vein tortuosity are thought to be caused by increases in vascular transmural pressure. We have attempted to determine the relationship between retinal vessel tortuosity, diameter, and transmural pressure by examining the effects of changes in transmural pressure on latex tubes with fixed ends. As the transmural pressure is raised, tube diameter increases, but tortuosity does not begin increasing until a critical pressure is reached. Above the critical pressure, tortuosity increases more rapidly than diameter. Our results support the above hypothesis and also suggest that at high transmural pressures, retinal vessel tortuosity is a more sensitive indicator than is the diameter of changes in retinal venous transmural pressure, but diameter is more sensitive than tortuosity at lower pressures.