Orbital fat swelling: A biomechanical theory and supporting model for spaceflight-associated neuro-ocular syndrome (SANS)

Spaceflight-Associated Neuro-ocular Syndrome (SANS) is a descriptor of several ocular and visual signs and symptoms which commonly afflicts those exposed to microgravity. We propose a new theory for the driving force leading to the development of Spaceflight-Associated Neuro-ocular Syndrome which is described via a finite element model of the eye and orbit. Our simulations suggest that the anteriorly directed force produced by orbital fat swelling is a unifying explanatory mechanism for Spaceflight-Associated Neuro-ocular Syndrome, as well as producing a larger effect than that generated by elevation in intracranial pressure. Hallmarks of this new theory include broad flattening of the posterior globe, loss of tension in the peripapillary choroid, decreased axial length, consistent with findings in astronauts. A geometric sensitivity study suggests several anatomical dimensions may be protective against Spaceflight-Associated Neuro-ocular Syndrome.

Determination of Dexamethasone in Milk by High Pressure Liquid Chromatography

A rapid and sensitive high pressure liquid chromatographic method for the analysis of dexamethasone (9α-fluoro-11β,17α,21-trihydroxy-16α-methylpregna-1,4-diene-3,20-dione) in milk has been developed. The corticosteroid can be quantitated at 20 ppb, with the limit of detectability estimated at 5 ppb. Recoveries ranged from 72 to 94%. After dexamethasone was injected into 5 Holstein-Friesian cows, no residues were found in milk, even after the first milking.

Characteristics of the cerebrospinal fluid pressure waveform and craniospinal compliance in idiopathic intracranial hypertension subjects

BACKGROUND

Idiopathic intracranial hypertension (IIH) is a condition of abnormally high intracranial pressure with an unknown etiology. The objective of this study is to characterize craniospinal compliance and measure the cerebrospinal fluid (CSF) pressure waveform as CSF is passively drained during a diagnostic and therapeutic lumbar puncture (LP) in IIH.

METHODS

Eighteen subjects who met the Modified Dandy Criteria, including papilledema and visual field loss, received an ultrasound guided LP where CSF pressure (CSFP) was recorded at each increment of CSF removal. Joinpoint regression models were used to calculate compliance from CSF pressure and the corresponding volume removed at each increment for each subject. Twelve subjects had their CSFP waveform recorded with an electronic transducer. Body mass index, mean CSFP, and cerebral perfusion pressure (CPP) were also calculated. T-tests were used to compare measurements, and correlations were performed between parameters.

RESULTS

Cerebrospinal fluid pressure, CSFP pulse amplitude (CPA), and CPP were found to be significantly different (p < 0.05) before and after the LP. CSFP and CPA decreased after the LP, while CPP increased. The craniospinal compliance significantly increased (p < 0.05) post-LP. CPA and CSFP were significantly positively correlated.

CONCLUSIONS

Both low craniospinal compliance (at high CSFP) and high craniospinal compliance (at low CSFP) regions were determined. The CSFP waveform morphology in IIH was characterized and CPA was found to be positively correlated to the magnitude of CSFP. Future studies will investigate how craniospinal compliance may correlate to symptoms and/or response to therapy in IIH subjects.

Visual outcomes following optic nerve sheath fenestration via the medial transconjunctival approach

This article determines the safety of optic nerve sheath fenestration (ONSF) for the treatment of patients with intracranial hypertension in the immediate 6-month post-operative period and its efficacy in reducing optic disk edema. Retrospective, non-comparative interventional case series. 207 eyes in 104 patients undergoing ONSF between the years 2005 and 2014. Papilledema grade based on modified Frisen scale and mean deviation of Humphrey visual field. 207 eyes of 104 patients (102 IIH, 2 IH due to dural sinus thrombosis) were included in the study. The patients were 96.1% female (N = 100) and 3.9% male (N = 4). The average patient age was 28.8 years (SD ± 9.5 years) and had a mean opening pressure of 39.85 cmH2O (SD ± 8.4 cmH2O). Mean follow-up period was 6.0 months (SD ± 5.9 months). Papilledema resolved in 76.1% of eyes at 1 week (N = 102 eyes), 75% of eyes at 1 month (N = 90 eyes), and 71% of eyes at 6 months (N = 94 eyes). Visual field comparison had a mean of the paired differences in MD at 1 week, 1 month, and 6 months of 1.59dB (P = 0.006), 2.53dB (P < 0.001), and 1.30dB (P = 0.016), respectively. ONSF is effective in reducing optic disk edema and does not cause vision loss in the 6-month post-operative period regardless of severity of IIH (as judged by elevation of opening pressure measured at pre-operative assessment).

Increased Ocular Pulse Amplitude Associated with Unilateral Dysgenesis of the Orbital Roof

Introduction

Two patients (one with neurofibromatosis type 1) presented with unilateral ocular pulsation.

Methods

A CT scan of the orbits revealed extensive dysgenesis of the orbital roof with herniation of the frontal lobe into the orbit in both cases. PASCAL dynamic contour tonometry was performed.

Results

The ipsilateral ocular pulse amplitude (OPA) was greater than the contralateral side, and the ocular pulse waveform morphology more closely approximated the known intracranial waveform in these patients.

Conclusions

We hypothesize that the greater OPA was due to stronger transmission of the intracranial pressure waveform amplitude and morphology in the absence of the orbital roof.

Cocaine-induced transmural myocardial infarction in a Yorkshire swine with normal coronary arteries: Evidence for microvascular and/or epicardial coronary artery spasm

Cocaine-induced myocardial infarction with normal coronary arteries is well documented in humans. The exact mechanism of action remains speculative. We report one case of cocaine-induced myocardial infarction with normal coronaries in one swine. Systemic hemodynamics and angiographic, electrocardiographic, echocardiographic, and histopathologic data are presented. Intravenous cocaine (1, 3, 10 mg/kg) produced significant decreases in mean arterial pressure, heart rate, stroke volume, coronary blood flow, and coronary reserve, whereas pulmonary artery diastolic pressure and coronary vascular resistances increased. Left anterior descending and left circumflex coronary artery cross-sectional area decreased by 31% and 64%, respectively, without localized vasospasm. Electrocardiographic changes occurred (3 mm ST elevation in leads II, III, AVF). Peak creatine phosphokinase was 17,220 IU/L. The echocardiogram revealed severe hypokinesis of the inferior wall and normal ventricular function. The animal survived the acute phase of the infarction and the swine was restudied 12 weeks later. Upon rechallenge, systemic and coronary hemodynamics shoved changes similar to those in the previous study. The swine developed ventricular fibrillation and expired after the 10 mg/kg cocaine dose. Macroscopic examination of the external surface of the heart revealed marked diffuse fibrosis in the posteroinferior and lateral left ventricular wall. Our data suggest that the infarct induced by cocaine may have resulted from severe vasoconstriction or spasm at the level of the microcirculation, and/or the epicardial coronary arteries, which shoved slight but significant narrowing throughout their lengths.

Ocular pressure waveform reflects ventricular bigeminy and aortic insufficiency

Ocular pulse amplitude (OPA) is defined as the difference between maximum and minimum intraocular pressure (IOP) during a cardiac cycle. Average values of OPA range from 1 to 4 mmHg. The purpose of this investigation is to determine the source of an irregular IOP waveform with elevated OPA in a 48-year-old male. Ocular pressure waveforms had an unusual shape consistent with early ventricular contraction. With a normal IOP, OPA was 9 mmHg, which is extraordinarily high. The subject was examined by a cardiologist and was determined to be in ventricular bigeminy. In addition, he had bounding carotid pulses and echocardiogram confirmed aortic insufficiency. After replacement of the aortic valve, the bigeminy resolved and the ocular pulse waveform became regular in appearance with an OPA of 1.6–2.0 mmHg. The ocular pressure waveform is a direct reflection of hemodynamics. Evaluating this waveform may provide an additional opportunity for screening subjects for cardiovascular anomalies and arrhythmias.

Sino-orbital spelunking: stalagmite formation in fibrous dysplasia with dystrophic calcification

Fibrous dysplasia (FD) involving the mid-face may be associated with cystic and other secondary changes that make diagnosis more difficult. We present a case of FD associated with a remote history of blunt facial trauma and extensive cystic changes involving the medial orbit and sinuses. An endoscopic exploration revealed "stalagmites" along the floor of the cystic cavity that were consistent with dystrophic calcification. This case was unusual given the degree of dystrophic calcification and the presence of sino-orbital stalagmites within the cystic cavity. Radiologic and pathologic features of the stalagmites are characterized.

Hidradenoma papilliferum of the orbit

PURPOSE

Hidradenoma papilliferum (HP) is a cystic lesion of apocrine gland origin that occurs most commonly in the perineal region. Although there are scattered reports of HP involving the eyelid, to our knowledge, we present the first case of HP of the orbit.

METHODS

A 63 year-old female presented with progressive left upper eyelid fullness over an 18 month period.

RESULTS

The lesion was excised via transconjunctival anterior orbitotomy without incident.

CONCLUSIONS

The pathologic features of HP are presented.

Pyogenic granuloma presenting as an orbital mass

Pyogenic granuloma (PG) of the eyelid and orbit is typically associated with trauma or surgery. We report a rare case of an orbital intraconal PG arising de novo in association with an orbital artery.

Cerebrospinal fluid outflow: an evolving perspective

Cerebrospinal fluid (CSF) serves numerous important functions in the central nervous system. Despite numerous reports characterizing CSF and its circulation in the subarachnoid space, our understanding of CSF outflow remains limited. Although initial work suggested that both arachnoid granulations and lymphatic capillaries shared in the role of CSF outflow, predominant work since then has focused on the arachnoid granulations. A growing body of recent evidence not only suggests the importance of both arachnoid granulations and lymphatic capillaries, but also additional contributions through transependymal passage likely share in the role of CSF outflow. Consideration of all mechanisms and pathways will help us to better understand the significance of CSF outflow, in health and disease. Here we review how the present concept of CSF outflow has evolved, including a historical review of significant findings and a discussion of the latest innovative developments.

Human arachnoid granulations Part I: a technique for quantifying area and distribution on the superior surface of the cerebral cortex

Background

The arachnoid granulations (AGs) are herniations of the arachnoid membrane into the dural venous sinuses on the surface of the brain. Previous morphological studies of AGs have been limited in scope and only one has mentioned surface area measurements. The purpose of this study was to investigate the topographic distribution of AGs on the superior surface of the cerebral cortex.

Methods

En face images were taken of the superior surface of 35 formalin-fixed human brains. AGs were manually identified using Adobe Photoshop, with a pixel location containing an AG defined as 'positive'. A set of 25 standard fiducial points was marked on each hemisphere for a total of 50 points on each image. The points were connected on each hemisphere to create a segmented image. A standard template was created for each hemisphere by calculating the average position of the 25 fiducial points from all brains. Each segmented image was mapped to the standard template using a linear transformation. A topographic distribution map was produced by calculating the proportion of AG positive images at each pixel in the standard template. The AG surface area was calculated for each hemisphere and for the total brain superior surface. To adjust for different brain sizes, the proportional involvement of AGs was calculated by dividing the AG area by the total area.

Results

The total brain average surface area of AGs was 78.53 ± 13.13 mm² (n = 35) and average AG proportional involvement was 57.71 × 10^-4 ± 7.65 × 10^-4. Regression analysis confirmed the reproducibility of AG identification between independent researchers with r² = 0.97. The surface AGs were localized in the parasagittal planes that coincide with the region of the lateral lacunae.

Conclusion

The data obtained on the spatial distribution and en face surface area of AGs will be used in an in vitro model of CSF outflow. With an increase in the number of samples, this analysis technique can be used to study the relationship between AG surface area and variables such as age, race and gender.

In Vitro Model of Cerebrospinal Fluid Outflow through Human Arachnoid Granulations

PURPOSE

To describe and validate an in vitro model of the arachnoid granulation (AG) outflow pathway for cerebrospinal fluid (CSF), by using human AG cells grown on a filter membrane support and perfused in a modified Ussing chamber at pressures analogous to normal human intracranial pressures.

METHODS

Human AG cells were grown, characterized, seeded onto filter membranes, and perfused in the physiologic (basal to apical, B-->A) or nonphysiologic (apical to basal, A-->B) directions. Cells were fixed under pressure after perfusion and prepared for electron microscopy (EM).

RESULTS

The average cellular hydraulic conductivity in the B-->A direction (10 total) was 4.52 +/- 0.43 microL/min per mm Hg/cm(2) with an average transcellular pressure decrease of 3.13 +/- 0.09 mm Hg. The average cellular hydraulic conductivity in the A-->B direction (six total) was 0.29 +/- 0.16 microL/min per mm Hg/cm(2) with an average transcellular decrease in pressure of 3.33 +/- 0.16 mm Hg. Cells perfused nonphysiologically showed a large number of dead and dying cells. EM postperfusion analysis showed that AG cells were integrally attached to the underlying filter membrane. Large extracellular cisternal spaces were visible between overlapping AG cells and vacuoles within the cytoplasm. It is possible that these spaces within and between cells represent pathways for transcellular and paracellular transport of fluid.

CONCLUSIONS

The results demonstrate that AG cells in vitro show a statistically significant greater flow rate and cellular hydraulic conductivity when perfused in the physiologic versus the nonphysiologic direction under normal intracranial pressures. These results suggest that this in vitro model of the AGs can accurately replicate the unidirectional flow of CSF in vivo.

Characterization of cytoskeletal and junctional proteins expressed by cells cultured from human arachnoid granulation tissue

BACKGROUND

The arachnoid granulations (AGs) are projections of the arachnoid membrane into the dural venous sinuses. They function, along with the extracranial lymphatics, to circulate the cerebrospinal fluid (CSF) to the systemic venous circulation. Disruption of normal CSF dynamics may result in increased intracranial pressures causing many problems including headaches and visual loss, as in idiopathic intracranial hypertension and hydrocephalus. To study the role of AGs in CSF egress, we have grown cells from human AG tissue in vitro and have characterized their expression of those cytoskeletal and junctional proteins that may function in the regulation of CSF outflow.

METHODS

Human AG tissue was obtained at autopsy, and explanted to cell culture dishes coated with fibronectin. Typically, cells migrated from the explanted tissue after 7-10 days in vitro. Second or third passage cells were seeded onto fibronectin-coated coverslips at confluent densities and grown to confluency for 7-10 days. Arachnoidal cells were tested using immunocytochemical methods for the expression of several common cytoskeletal and junctional proteins. Second and third passage cultures were also labeled with the common endothelial markers CD-31 or VE-cadherin (CD144) and their expression was quantified using flow cytometry analysis.

RESULTS

Confluent cultures of arachnoidal cells expressed the intermediate filament protein vimentin. Cytokeratin intermediate filaments were expressed variably in a subpopulation of cells. The cultures also expressed the junctional proteins connexin43, desmoplakin 1 and 2, E-cadherin, and zonula occludens-1. Flow cytometry analysis indicated that second and third passage cultures failed to express the endothelial cell markers CD31 or VE-cadherin in significant quantities, thereby showing that these cultures did not consist of endothelial cells from the venous sinus wall.

CONCLUSION

To our knowledge, this is the first report of the in vitro culture of arachnoidal cells grown from human AG tissue. We demonstrated that these cells in vitro continue to express some of the cytoskeletal and junctional proteins characterized previously in human AG tissue, such as proteins involved in the formation of gap junctions, desmosomes, epithelial specific adherens junctions, as well as tight junctions. These junctional proteins in particular may be important in allowing these arachnoidal cells to regulate CSF outflow.

Depsipeptide inhibits migration of primary and metastatic uveal melanoma cell lines in vitro: a potential strategy for uveal melanoma

Uveal melanoma (UM) is a highly malignant primary intraocular tumour in adults that has a high mortality rate due to haematogenous dissemination. The migration of UM cells through the basement membrane requires the presence of proteolytic enzymes, such as matrix metalloproteinases (MMPs). The expression of MMP-2, MMP-9 and membrane type-1/MMP (MT-1/MMP) in UM cells is a known risk factor for metastatic disease. We tested the effect of depsipeptide (DP) on UM cell migration and the level and activity of MMP-2, MMP-9, MT-1/MMP and tissue inhibitors of matrix metalloproteinases 1 and 2 (TIMP-1 and TIMP-2). Three primary and two metastatic (liver metastasis) UM cell lines were treated with DP (0, 1, 5 and 10 nmol/l) for 24 h. Migration of UM cells was studied in modified Boyden migration chambers for 24 h and only viable cells on both sides of the membrane were counted. Enzyme-linked immunosorbent assays (ELISAs) were used to quantify the level of MMP-2, MMP-9, MT-1/MMP, TIMP-1 and TIMP-2 after the cells had been exposed to DP (0, 1, 5 and 10 nmol/l) for 24 h. In addition, the activities of MMP-2, MMP-9 and MT-1/MMP were determined after DP treatment. A dose-dependent decrease in the migration of viable UM cells was observed for primary and metastatic cell lines (30-50% inhibition). We detected a dose-dependent: (1) decrease in the protein level of MMP-2, MMP-9 and MT-1/MMP; (2) decrease in the activity of MMP-2, MMP-9 and MT-1/MMP; and (3) increase in the protein level of TIMP-1 and TIMP-2. It can be concluded that DP is a potent inhibitor of primary and metastatic UM cell migration in vitro. Our data suggest that this inhibition is mediated by the downregulation of MMPs and the upregulation of TIMPs. DP may be a valuable adjunctive treatment modality for primary and metastatic UM in humans.

Somatostatin inhibits IGF-1 mediated induction of VEGF in human retinal pigment epithelial cells

Neovascularization stimulated by IGF-1 mediated induction of vascular endothelial growth factor (VEGF) is one of the leading causes of blindness in humans. It plays a central role in the pathogenesis of proliferative diabetic retinopathy (DR), neovascular glaucoma, exudative age-related macular degeneration (AMD) and retinopathy of prematurity. Neovascularization is a multi-step process that involves complex interactions of a variety of mitogenic factors such as VEGF and IGF-I which are produced locally in the human eye by a variety of cells including retinal pigment epithelial (RPE) cells, retinal capillary pericytes, endothelial cells, Mueller cells and ganglion cells. We hypothesized that somatostatin would inhibit the IGF-1 signal transduction pathway in RPE cells, resulting in decreased VEGF production. We have observed expression of somatostatin receptor protein in retinal pigment epithelial (RPE) cells of the human eye using immunohistochemistry and have confirmed expression of somatostatin receptors in cultured human RPE cells using reverse transcriptase-PCR. IGF-1 induced a dose dependent increase in IGF-1R phosphorylation and in VEGF mRNA levels in cultured human RPE cells. Somatostatin and octreotide, a somatostatin analogue, inhibited IGF-1 receptor (IGF-1R) phosphorylation and decreased VEGF production. Both IGF-1R phosphorylation and accumulation of VEGF mRNA were inhibited by physiological levels of somatostatin and octreotide (1 nM). These results demonstrate somatostatin and octreotide mediated attenuation of both IGF-1R signal transduction and VEGF mRNA accumulation via somatostatin receptor type 2 (sst2). Furthermore, these data suggest a rationale for the use of octreotide as a prophylactic and therapeutic option in disease states that cause ocular neovascularization.

Depsipeptide (FR901228) inhibits proliferation and induces apoptosis in primary and metastatic human uveal melanoma cell lines

PURPOSE

Uveal melanoma (UM) is the most common primary malignant ocular tumor in adults. No effective chemotherapy regimens are available for either intraocular or metastatic uveal melanoma. Therefore, the ability of the histone deacetylase inhibitors (HDACIs), depsipeptide, sodium butyrate (NaB) and trichostatin A (TSA), to induce apoptosis and inhibit cell growth of UM cell lines in vitro was examined.

METHODS

Three primary and two metastatic UM cell lines were treated in vitro with different concentrations of histone deacetylase inhibitors (HDACIs). Cell proliferation was studied in 24-well plates. Induction of apoptosis was studied by flow cytometry. Changes in gene expression of Fas/FasL, p21(Waf/Cip1), and p27(Kip1) were studied by RT-PCR. Western blot analysis was used to study histone acetylation, Fas/FasL, p21(Waf/Cip1), p27(Kip1) and caspase-3 protein levels. Real-time PCR was used to study changes in bcl-2/bax gene expression.

RESULTS

A dose-dependent increase in histone acetylation was observed in all cell lines. This corresponded to significant inhibition of cell growth and induction of apoptosis in all melanoma cell lines in a concentration-dependent manner. Western blot analysis revealed dose-dependent increases in the amount of caspase-3, Fas/FasL, p21(Waf/Cip1), and p27(Kip1) proteins. However, no changes in bcl-2/bax gene expression were detected by real-time PCR.

CONCLUSIONS

HDACIs are potent inhibitors of primary and metastatic UM cell growth in vitro. The apoptosis is probably mediated through the Fas/FasL signaling pathway, whereas bcl-2 appears not to be involved. These data support further clinical evaluation of depsipeptide and other HDACIs in patients with primary and metastatic UM.

Evidence-based care for depression in Maine: dissemination of the Kaiser Permanente Nurse Telecare Program

This paper describes the program model, implementation and preliminary results from a dissemination of a nurse case management program for treating depression in primary care. The program design was modeled after the Kaiser Permanente Nurse TeleCare program, which in a randomized clinical trial had previously demonstrated significant improvement in depression outcomes and patient satisfaction over usual care. As illustrated in this pilot by patient outcomes measured using the Hamilton Depression Rating Scale, the SF-12 Mental Health Composite Score, and the Work Role, Household and Leisure Time Functioning, the authors believe that it is possible to implement successful interventions in smaller primary care practices in community-based settings.

Expression of somatostatin receptors 1 and 2 in human choroid plexus and arachnoid granulations: implications for idiopathic intracranial hypertension

OBJECTIVE

To investigate the localization of somatostatin receptor types 1 and 2 in human choroid plexus (CP) and arachnoid granulations (AGs) by immunohistochemistry.

METHODS

A prospective study was performed in an institutional setting. Immunohistochemistry was performed on 15 samples of CP and 12 samples of AGs from 15 patients who died with no signs or symptoms of intracranial disease (age range, 52-81 years). The CP samples were dissected from the lateral ventricles and AG samples were dissected from the superior sagittal sinus.

RESULTS

We demonstrated the presence of both somatostatin receptor types 1 and 2 in all samples of normal human CP and AGs.

CONCLUSIONS

Analogous to their demonstration and to their function in kidney and ocular tissues, these receptors may be involved in the processes of cerebrospinal fluid production and absorption, and may play a role in the increased intracranial pressure of idiopathic intracranial hypertension.

CLINICAL RELEVANCE

Somatostatin analogues have been used to treat idiopathic intracranial hypertension, a disorder of cerebrospinal fluid homeostasis. Data are scarce regarding the cell-specific distribution of somatostatin receptors in normal human CP and AGs, the sites of cerebrospinal fluid production and egress.

The wayward implant: orbital silicone plate extrusion associated with squamous epithelial downgrowth and infection

We report an unusual case of orbital implant migration in which the silicone plates were found to be enveloped in a pseudocapsule surprisingly infected and lined by squamous epithelium of probable conjunctival origin. An epithelial 'plug' found in the inferior fornix portion of the pseudocapsule might have been responsible for bacterial entry into the cavity. We discuss the literature regarding pseudocapsule formation around silicone implants and the phenomenon of capsular contracture. Both the infection and the epithelial downgrowth may have facilitated the implant migration.

Spontaneous globe luxation associated with contact lens placement

PURPOSE

Globe luxation, characterized as the anterior dislocation of the eyeball beyond retracted lids, presents a dramatic clinical picture. It is an uncommon event and can produce anxiety in both the patient and the physician. The purpose of this article is to present a case of spontaneous globe luxation which occurred with attempted contact lens placement.

METHODS

A case report and literature review are presented.

RESULTS

Manual reduction of the globe required conscious sedation in the emergency room. Diffuse superficial punctate keratitis resolved completely with no visual sequelae.

DISCUSSION

The clinical features, epidemiology, risk factors, complications and treatments of globe luxation are presented. Eye care specialists who fit and dispense contact lenses should be aware of risk factors associated with globe luxation. A step-wise plan for management is presented, in hope of limiting patient discomfort, recurrence, and perhaps long-term visual impairment.

Somatostatin receptor gene expression in human ocular tissues: RT-PCR and immunohistochemical study

PURPOSE

Somatostatin (SST) analogues have been used to treat proliferative diabetic retinopathy, pseudotumor cerebri, thyroid orbitopathy, and cystoid macular edema. There is a paucity of published data in regards to cell-specific distribution of SST receptors (SSTR) in normal human eye tissues. Gene expression for all five known SSTRs in normal human ciliary body/iris, retina, choroid, and cultured retinal pigment epithelial (RPE) cells were studied.

METHODS

mRNA was isolated from human ocular tissues (iris/ciliary body, retina, and choroid) dissected from eight pairs of normal eyes (9-62 years) and from RPE cells grown in culture. RT-PCR was done for all five SSTRs in all analyzed tissues. Immunohistochemistry for SSTR1 and SSTR2 was performed on eight pairs of normal human eyes (28-74 years) imbedded in paraffin.

RESULTS

SSTR1 to 5 genes are expressed in retina, SSTR1 and SSTR2 genes in cultured RPE cells, and SSTR1, 2, and 4 in ciliary body and choroid. SSTR1 and SSTR2 immunoreactivity (-ir) was observed on a variety of cells within all analyzed tissues including cornea, iris, trabecular meshwork, Schlemm's canal, ciliary processes, ciliary muscle, retina, choroid, cultured RPE cells, and optic nerve.

CONCLUSIONS

SSTR genes are widely expressed in normal human eye tissues, with genes for SSTR1 and SSTR2 being the most widely expressed. Genes for all SSTRs are expressed in retina. SSTR1-ir and SSTR2-ir were observed in all analyzed ocular tissues. Detailed knowledge of SSTRs distribution and function in the human eye will result in a better understanding of their role in health and disease.

Chemical, physical, and environmental properties of pelleted newspaper compared to wheat straw and wood shavings as bedding for horses

Two experiments were conducted comparing pelleted recycled newspaper (PN) to wheat straw (S) and kiln-dried pine wood shavings (WS) as an animal bedding material. Adult horses housed 20 to 21 h/d in boxstalls served as the animal model for comparisons. In Exp. 1 eight boxstalls, each housing one horse, were each bedded with two types of PN (0.32 and 0.64 x 2.54 cm), S, and WS over four 5-d periods (replicated 4 x 4 Latin square). Initial amounts of bedding materials surpassed most commercial conditions, but stalls were cleaned daily of feces only and additional clean bedding was added as needed to maintain animal cleanliness, thus challenging the bedding properties of each material. In Exp. 2 nine boxstalls were bedded with PN (0.32 x 2.54 cm), S, and WS over three 14-d periods (three 3 x 3 Latin squares) during summer and autumn. Feces and wet spots were removed daily and clean bedding was added to reestablish working volume and simulate commercial conditions. In Exp. 1 and 2 daily additions of clean bedding varied (P < 0.05) with material (S > WS > PN). The higher water-holding capacity of PN and WS contributed to fewer bedding replacements. Usage of each material was greater (P < 0.05) during the autumn; PN had the greatest increase. Type of material and season also influenced bedding environment. Bedding pH increased (P < 0.05) with use and was highest in PN and lowest in S. Higher concentrations of breathable NH3 N were present in stalls bedded with PN and during autumn. Higher pH of used PN and decreased ventilation due to closed doors and windows during autumn were contributing factors. Season, type of bedding, and duration of its use affected (P < 0.05) numbers as well as species of microorganisms present in the breathing zone, nasal cavity, and on the leg of the horse. Clean and used WS contained greater (P < 0.05) quantities of particle fines, but with 5 d of use, particle fines in PN also increased. Quantities of breathable dust during cleaning of stalls varied (P < 0.05) with material and duration of its use; dust peaked at d 7 with PN but continued to decrease with S and to increase with WS through d 14. These data indicate that management of bedding materials varies with type of material and season of year. Use of PN as a bedding material has high potential.

Importance of an intact growth hormone/insulin-like growth factor 1 axis for normal post-infarction healing: studies in dwarf rats

Treatment with GH attenuates remodeling and improves left ventricular function in the setting of experimental heart failure following coronary ligation. This study was designed to test the hypothesis that an intact GH/insulin-like growth factor 1 (IGF-1) axis is required for normal myocardial infarction healing. Myocardial infarction was induced by coronary ligation in GH-deficient dwarf rats and in age-matched controls. In dwarf rats, serum IGF-1 levels were reduced by 50%, and grow rate was 50% less than normal littermates, although no differences in myocardial IGF-1 messenger RNA levels were observed compared with controls. All rats underwent transthoracic echocardiography at baseline, 2 weeks, and 6 weeks after myocardial infarction. Left ventricular end-diastolic pressure was obtained by in vivo closed chest catheterization. At 6 weeks, both infarcted groups exhibited similar myocardial infarction size at transthoracic echocardiography and at morphometric histology. In both groups with myocardial infarction, there was significant left ventricular dilation and reduced systolic function. However, the extent of remodeling as assessed by the increase in end-diastolic dimension (%Delta + 36 +/- 5 vs. +19 +/- 4; P: < 0.01) and depression of function (%Delta fractional shortening -12 +/- 2 vs. -7 +/- 1; P: < 0.01) were both greater in the dwarf group. Furthermore, dwarf rats failed to develop compensatory hypertrophy of noninfarcted posterior wall (%Delta posterior wall +5 +/- 1 vs. +15 +/- 3; P: < 0.01). Therefore, pathologic left ventricular remodeling and functional loss following myocardial infarction is more marked in conditions of GH deficiency. An intact GH/IGF-1 axis appears necessary for a normal response to myocardial infarction injury in the rat.

Intraorbital rupture of a cavernous internal carotid artery aneurysm: therapeutic options

PURPOSE

To describe the use of an endovascular therapeutic technique in the management of a giant carotid cavernous aneurysm.

METHODS

We reviewed the clinical and neuroradiologic findings of a patient with an unusual case of carotid cavernous aneurysm and intraorbital rupture. The medical literature was searched for similar cases and to review the use of endovascular techniques.

RESULTS

The patient was treated by balloon occlusion of the left internal carotid artery.

CONCLUSIONS

Endovascular techniques can be used to treat complex giant cranioorbital cavernous aneurysms.

Echocardiographic assessment of cardiac morphology and function in mutant dwarf rats

Although the mutant dwarf rat has been proposed as a model of growth hormone (GH) deficiency, few studies have addressed its cardiovascular abnormalities. Therefore, the aim of the present study was to investigate cardiac structure and function in mutant dwarf rats in vivo before and after chronic GH administration, by means of transthoracic Doppler echocardiography. To this purpose, forty 90-day-old female dwarf rats were randomized to receive either GH treatment or placebo. Twenty age-and sex-matched Lewis rats (200-250 g) served as the control group. All rats underwent echocardiograms before receiving any drug and after 3 weeks of therapy. Echocardiographically detected left ventricular mass indexed to tibial length was reduced by 41% in dwarf rats compared to the control group. Such relative cardiac atrophy was also evident at the myocyte level, and was fully reversible after GH therapy. In contrast to the control group, dwarf rats also showed a reduction of left ventricular diastolic volumes normalized to tibial length and impaired cardiac performance as suggested by the reduction of cardiac index, abnormal stress-shortening relations, and a significant elevation of total peripheral vascular resistance. All these abnormalities were reversible upon GH therapy for 3 weeks. In conclusion, GH plays an important role in maintaining a normal cardiac structure and function. Since the observed changes are similar to those seen in GH-deficient men, the mutant dwarf rat represents a faithful animal model of GH deficiency.

Intersession repeatability of macular thickness measurements with the Humphrey 2000 OCT

PURPOSE

This study was designed to determine intersession repeatability of measurements of macular thickness made with a commercially available optical coherence tomography (OCT) system. The images that can be routinely acquired with the commercial instrument differ significantly in quality from the images in the literature, which have mostly been acquired on prototype systems.

METHODS

Multiple OCT images of the nasal macula were obtained from the right eye during three independent measuring sessions, using the Humphrey 2000 OCT system (Humphrey, San Leandro, CA). Twenty-six volunteers with no history of ocular disease participated in this investigation. Eyes in all subjects were undilated during scan acquisition. Scans were horizontal, 3 mm long, and through the fovea. Five scans were used from each session, for a total of 15 scans per subject. Retinal boundaries were automatically detected using custom software. Statistical software was used to calculate intersession and intrasession repeatability. Manual correction was performed on the automatically detected boundaries, and a second analysis was performed using these boundaries.

RESULTS

When no manual correction of boundaries was performed, there were no significant effects between different sessions (P = 0.529) or between different scans within the same session (P = 0.509). Average retinal thickness was found to be 274 +/- 17 microm for a 1-mm long region 0.75 mm from the fovea. Individual scan averages differed from overall patient averages by 0 +/- 4.3 microm (99% confidence interval, 11.2 microm).

CONCLUSIONS

OCT measurements of macular thickness made with the Humphrey 2000 OCT system are repeatable over different sessions with an expected variation of less than 11 microm (99% confidence interval).

Visual loss and central venous catheterization: cortical blindness and hemianopsia after inadvertent subclavian artery entry

A case of presumed embolic transient ischemic episodes and multifocal infarcts to the occipital and parietal cortices and the cerebellum of a young woman with ulcerative colitis is reported. These episodes were manifested by multifocal neurologic deficits including cortical blindness, visual hallucinations, and homonymous hemianopsia. They correlated with parenteral nutrition via a central line, presumed venous, but found to be in the subclavian artery. The complications of central venous lines are reviewed. The need for attention to neighborhood structures and unexpected symptoms, in view of the less well-recognized arterial embolic complications is emphasized.

Chronic N(G)-nitro-L-arginine methyl ester-induced hypertension : novel molecular adaptation to systolic load in absence of hypertrophy

BACKGROUND

Chronic N(G)-nitro-L-arginine methyl ester (L-NAME), which inhibits nitric oxide synthesis, causes hypertension and would therefore be expected to induce robust cardiac hypertrophy. However, L-NAME has negative metabolic effects on protein synthesis that suppress the increase in left ventricular (LV) mass in response to sustained pressure overload. In the present study, we used L-NAME-induced hypertension to test the hypothesis that adaptation to pressure overload occurs even when hypertrophy is suppressed.

METHODS AND RESULTS

Male rats received L-NAME (50 mg. kg(-1). d(-1)) or no drug for 6 weeks. Rats with L-NAME-induced hypertension had levels of systolic wall stress similar to those of rats with aortic stenosis (85+/-19 versus 92+/-16 kdyne/cm). Rats with aortic stenosis developed a nearly 2-fold increase in LV mass compared with controls. In contrast, in the L-NAME rats, no increase in LV mass (1. 00+/-0.03 versus 1.04+/-0.04 g) or hypertrophy of isolated myocytes occurred (3586+/-129 versus 3756+/-135 microm(2)) compared with controls. Nevertheless, chronic pressure overload was not accompanied by the development of heart failure. LV systolic performance was maintained by mechanisms of concentric remodeling (decrease of in vivo LV chamber dimension relative to wall thickness) and augmented myocardial calcium-dependent contractile reserve associated with preserved expression of alpha- and beta-myosin heavy chain isoforms and sarcoplasmic reticulum Ca(2+) ATPase (SERCA-2).

CONCLUSIONS

When the expected compensatory hypertrophic response is suppressed during L-NAME-induced hypertension, severe chronic pressure overload is associated with a successful adaptation to maintain systolic performance; this adaptation depends on both LV remodeling and enhanced contractility in response to calcium.

Abnormal cardiac function in the streptozotocin-induced non-insulin-dependent diabetic rat: noninvasive assessment with doppler echocardiography and contribution of the nitric oxide pathway

OBJECTIVES

We sought to evaluate in vivo and in vitro left ventricular (LV) geometry and function in streptozotocin-induced diabetic rats and the possible role of the nitric oxide (NO) pathway.

BACKGROUND

Diabetes results in cardiac dysfunction; however, the specific abnormalities are unknown. Because decreased NO contributes to abnormal vascular function in diabetics, we hypothesized that NO pathway abnormalities may contribute to diabetic cardiomyopathy.

METHODS

Control rats and those with non-insulin-dependent diabetes mellitus (NIDDM) underwent echocardiography, hemodynamic assessment, isolated heart perfusion and measurement of exhaled NO and LV endothelial constitutive nitric oxide synthase (ecNOS).

RESULTS

Diabetic rats had increased LV mass (3.3 +/- 0.6 vs. 2.6 +/- 0.3 g/g body weight [BW], p < 0.001) and cavity dimensions (diastolic 2.0 +/- 0.1 vs. 1.8 +/- 0.2 cm/cm tibial length [TL], p < 0.05). Diabetic rats had prolonged isovolumic relaxation time (IVRT) (40 +/- 8 vs. 26 +/- 6 ms, p < 0.0001), increased atrial contribution to diastolic filling (0.47 +/- 0.09 vs. 0.30 +/- 0.08 m/s, p < 0.0001), and elevated in vivo LV end-diastolic pressure (7 +/- 6 vs. 2 +/- 1 mm Hg, p = 0.04). Diabetic rats had increased chamber stiffness. Shortening was similar in both groups, despite reduced meridional wall stress in diabetics, suggesting impaired systolic contractility. Exhaled NO was lower in diabetic rats (1.8 +/- 0.2 vs. 3.3 +/- 0.3 parts per billion, p < 0.01) and correlated with Doppler LV filling. The ecNOS was similar between the groups.

CONCLUSIONS

Diabetic cardiomyopathy is characterized by LV systolic and diastolic dysfunction, the latter correlating with decreased exhaled NO. The NO pathway is intact, suggesting impaired availability of NO as contributor to cardiomyopathy.

Orbital "shanking": a unique prison injury

The purpose of this paper is to describe orbitocranial penetration due to "shanking", a common mode of assault in prison facilities. We report the case of a prisoner who presented with orbital apex syndrome 5 days after an assault. He died 9 days after surgical removal of the "shank" due to a presumed ruptured traumatic aneurysm. Physicians who evaluate prisoners must maintain a high index of suspicion for penetrating injuries. The entrance site is often inconspicuous and the history may be limited in this unique population.

Cardiovascular abnormalities in transgenic mice with reduced brown fat: an animal model of human obesity

BACKGROUND

A new model of murine obesity has recently been developed through transgenic ablation of brown adipose tissue that manifests typical metabolic complications of obesity, including insulin resistance and non-insulin-dependent diabetes mellitus. The cardiovascular phenotype has not been defined.

METHODS AND RESULTS

Transthoracic echocardiography, aortic catheterization, isolated whole-heart studies, and morphometric histology defined cardiac structure and function in 30 transgenic mice with reduced brown fat and 30 matched wild-type controls. Obesity was indicated by a 77% increase in body weight and was accompanied by elevated systemic pressures (mean aortic blood pressure 85+/-1 versus 66+/-2 mm Hg; P<0.01), left ventricular dilation and hypertrophy (mass/body weight 4.0+/-0.2 versus 2.7+/-0.3 mg/g; P<0.01), and high cardiac output (cardiac index 3.2+/-0.4 versus 2.4+/-0.1 mL x kg(-1) x min(-1); P<0.01). Baseline functional parameters assessed in vitro were not different, but after imposition of zero-flow ischemia, significant relaxation impairment developed in obese mice. Although morphometrically determined myocyte diameters were similar, the percentage of interstitial fibrosis was significantly increased in transgenic mice compared with wild-type controls (7.5+/-2% versus 4. 2+/-0.2%; P<0.01).

CONCLUSIONS

Transgenic ablation of brown adipose tissue is associated not only with obesity but also with systemic hypertension, left ventricular hypertrophy with eccentric remodeling and fibrosis, and high cardiac output, a unique constellation of findings strikingly similar to that seen in human obesity. Mice with reduced brown fat may serve as a new model for the cardiovascular morbid complications associated with obesity in humans.

Left atrial appendage anatomy and function: short term response to sustained atrial fibrillation

OBJECTIVE

To determine whether there is significant atrial or atrial appendage enlargement or functional remodelling as a result of one to two months of sustained atrial fibrillation, a duration similar to that experienced by patients undergoing warfarin anticoagulation before elective cardioversion.

METHODS

To test the hypothesis that left atrial and left atrial appendage enlargement develop as a result of short term atrial fibrillation, serial anatomical and functional indices were measured using transoesophageal echocardiography (TOE) in 20 patients with recent onset atrial fibrillation (14 men, six women; mean (SEM) age 67 (2) years). Serial TOE was performed 2.5 months apart in patients with sustained atrial fibrillation.

RESULTS

There was no significant change in left atrial area (23.7 cm(2) to 24.1 cm(2), p = 0.98); length (5.7 cm to 5.7 cm, p = 0.48); width (5.2 cm to 5.2 cm, p = 0. 65); volume (83 cm(3) to 87 cm(3), p = 0.51) or left atrial appendage area (7.9 cm(2) to 8.1 cm(2), p = 0.89); length (4.6 cm to 4.5 cm, p = 0.8); or width (2.5 to 2.4 cm, p = 0.87). Peak left atrial appendage velocity ejection (0.2 m/s to 0.2 m/s, p = 0.57), and presence of severe spontaneous echo contrast in the left atrial appendage (n = 15 (75%) to n = 13 (72%)) were also not significantly different. There was no correlation between changes in left atrial or left atrial appendage dimensions.

CONCLUSIONS

In the setting of sustained atrial fibrillation, significant left atrial and left atrial appendage functional and anatomical remodelling do not occur with atrial fibrillation of a duration similar to that used for conservative anticoagulation in preparation for cardioversion.

Gender differences in postinfarction left ventricular remodeling

OBJECTIVE

Previous studies suggest that gender affects the adaptive responses of the heart to some forms of cardiac overload. It is unknown whether gender influences left ventricular (LV) remodeling after myocardial infarction (MI).

METHODS

We performed transthoracic echocardiographic-Doppler examinations in age-matched male (n = 17) and female (n = 16) rats before, and 1 and 6 weeks after transmural MI or sham surgery.

RESULTS

Following large MI (male = 45 +/- 1% LV circumference vs. female = 48 +/- 4%, p = NS), both male and female rats developed progressive LV dilatation. Infarctions caused a similar degree of global and regional LV systolic dysfunction in males and females. Male rats had significant increases in the thickness of the noninfarcted posterior wall by 6 weeks after MI. However, posterior wall thickness did not change in the infarcted female rats. Average myocyte diameter in the noninfarcted region of the heart was also greater in male than female MI rats. The combination of increased cavity size with little change in wall thickness resulted in a greater decline in relative wall thickness in the female rats compared to the males. Male rats with MI showed progressively restricted LV diastolic filling as assessed by transmitral Doppler recordings. Female rats had less of an increase in the ratio of early to late transmitral velocities and less of an increase in the E wave deceleration rate after MI.

CONCLUSIONS

Female rats showed a different pattern of LV remodeling than males with less of an increase in thickness of the noninfarcted portions of the left ventricle than males, but comparable LV cavity enlargement and systolic dysfunction. Despite similar infarct size, females developed less pronounced abnormalities of LV diastolic filling. We hypothesize that the gender-related differences in postinfarction LV remodeling may contribute to the different LV filling patterns, and might ultimately relate to differences in clinical outcome.

Effects of propranolol treatment on left ventricular function and intracellular calcium regulation in rats with postinfarction heart failure

1. Chronic treatment with beta-adrenergic blocking agents can improve survival in patients with heart failure. The mechanisms underlying the beneficial effects and whether these effects are generalizable to ischaemic heart failure are unresolved. 2. We performed echocardiographic-Doppler examinations in rats (n=28) 1 and 6 weeks after myocardial infarction (MI) or sham surgery. Rats were randomized to no treatment or propranolol (500 mg/l in drinking water) after the first echocardiogram. Isometric contractions and intracellular Ca transients were recorded simultaneously in noninfarcted left ventricular (LV) papillary muscles. 3. Untreated MI rats had significant LV dilatation (10.6+/-0.4* vs 8.9+/(-0.3) mm, MI vs control), impaired systolic function (fractional shortening=11+/-2* vs 38+/-2%), and a restrictive LV diastolic filling pattern. MI rats receiving propranolol had similar LV chamber sizes (10.6+/(-0.5) mm) and systolic function (13+/(-2%). The propranolol treated animals had higher LV end-diastolic pressures (27+/-2* vs 20+/(-3 mmHg) and a more restricted LV diastolic filling pattern (increased ratio of early to late filling velocities and more rapid E wave deceleration rate). Contractility of papillary muscles from untreated MI rats was depressed (1.6+/(-0.3) vs 2.4+/(0.5 g mm(-2). In addition, Ca transients were prolonged and the inotropic response to isoproterenol was blunted. Propranolol treatment did not improve force development (1.6+/(-0.3 g mm(-2) or the duration of Ca transients during isoproterenol stimulation. 4. Chronic propranolol treatment in rats with postinfarction heart failure did not improve LV remodeling or systolic function. LV diastolic pressures and filling patterns were worsened by propranolol. Treatment also did not produce appreciable improvement in contractility, intracellular Ca regulation or beta-adrenergic responsiveness in the noninfarcted myocardium.

Suck and spit, don't blow: orbital emphysema after decompression surgery

PURPOSE

To describe the occurrence of vision-threatening orbital emphysema in patients awakening from orbital decompression surgery and to assess risk factors and preventive measures.

DESIGN

Small noncomparative case series.

PARTICIPANTS

Three patients undergoing bilateral orbital two-wall decompression experienced significant orbital emphysema associated with persistent coughing and Valsalva at the time of extubation.

INTERVENTION

In two patients, symptoms resolved with simple observation, whereas one patient required sedation, topical anesthesia around the endotracheal tube, and needle decompression of trapped air.

MAIN OUTCOME MEASURES

Visual acuity, pupils, visual fields, and sensorimotor examination.

RESULTS

No patient experienced a permanent deficit of visual or sensorimotor function.

CONCLUSIONS

Acute orbital emphysema can occur after orbital decompression surgery despite the large bony opening created. Violent coughing spells at the time of extubation are more common in patients with a history of heavy tobacco use and may be causative. Opening the periorbita may be another specific predisposing risk factor. Knowledge of this dangerous phenomenon, along with appropriate perioperative management, may prevent this complication from occurring.

Gender differences in molecular remodeling in pressure overload hypertrophy

OBJECTIVES

The objective of this study was to examine gender differences in left ventricular (LV) function and expression of cardiac genes in response to LV pressure overload due to ascending aortic stenosis in rats.

BACKGROUND

Clinical studies have documented gender differences in the pattern of adaptive LV hypertrophy. Whether these differences result from intrinsic differences in molecular adaptation to pressure overload between men and women, or are related to other factors is not known.

METHODS

Male (n = 8) and female (n = 8) Wistar rats underwent ascending aortic stenosis and were studied 6 weeks after banding with gender-matched control rats (male n = 7; female n = 7). The LV contractile reserve was examined in isolated hearts from each group. We compared LV messenger ribonucleic acid (mRNA) levels of atrial natriuretic factor (ANF), beta-myosin heavy chain, sarcoplasmic reticulum Ca2+-adenosine triphosphatase (ATPase) and Na+-Ca2+ exchanger. Reverse transcriptase polymerase chain reaction was used to identify estrogen receptor transcript in cardiac myocytes and LV tissue.

RESULTS

The magnitude of LV hypertrophy (LVH) and systolic wall stress were similar in male and female animals with LVH. Male LVH hearts demonstrated a depressed contractile reserve; in contrast, contractile reserve was preserved in female LVH hearts. The expression of beta-myosin heavy chain and ANF mRNA was greater in male versus female LVH hearts. Sarcoplasmic reticulum Ca2+-ATPase mRNA levels were depressed in male LVH but not in female LVH compared with control rats, and Na+-Ca2+ exchanger mRNA levels were increased similarly in both male and female LVH hearts. Estrogen receptor transcript was detected in both adult male and female cardiac myocytes and LV tissue.

CONCLUSIONS

There are significant gender differences in the LV adaptation to pressure overload despite a similar degree of LVH and systolic wall stress in male and female rats. There is the potential for estrogen signaling through the adult myocyte estrogen receptor in both male and female rats to contribute to gender differences in gene expression in pathologic hypertrophy.

Diagnosis of polycystic ovary syndrome

The clinical features of polycystic ovary syndrome (PCOS) include hirsutism and irregular menses, which are the results of ovarian hyperandrogenism and chronic, unopposed estrogen secretion. The discovery that most women with PCOS are insulin-resistant and have compensatory hyperinsulinemia, with increased risk for type 2 diabetes mellitus, designates this condition as a reproductive-metabolic disorder. That the symptoms of PCOS may be mimicked by other endocrine disorders of the ovary and adrenal glands warrants careful evaluation to exclude these associated conditions.

Hypertrophic remodeling: gender differences in the early response to left ventricular pressure overload

OBJECTIVES

To identify gender differences in left ventricular remodeling, hypertrophy, and function in response to pressure overload due to ascending aortic banding in rats.

BACKGROUND

Gender may influence the adaptation to pressure overload, as women with aortic stenosis have greater degrees of left ventricular hypertrophy and better left ventricular function than men.

METHODS

Fifty-two weanling rats underwent ascending aortic banding (16 males, 18 females), or sham surgery (9 males, 9 females). At 6 and 20 weeks, rats underwent transthoracic echo Doppler studies, and closed-chest left ventricular pressures with direct left ventricular puncture. Perfusion-fixed tissues from eight rats were examined morphometrically for myocyte cross-sectional area and percent collagen volume.

RESULTS

At 6 weeks after aortic banding, left ventricular remodeling, extent of hypertrophy, and function appeared similar in male and female rats. At 20 weeks, male but not female rats showed an early transition to heart failure, with onset of cavity dilatation (left ventricular diameter=155% vs. 121% of same-sex sham), loss of concentric remodeling (relative wall thickness=102% vs. 139% of sham), elevated wall stress (systolic stress=266% vs. 154% of sham), and diastolic dysfunction (deceleration of rapid filling=251% vs. 190% of sham). Left ventricular systolic pressures were higher in female compared with male rats (186+/-20 vs. 139+/-13 mm Hg), while diastolic pressures tended to be lower (14+/-4 vs. 17+/-4 mm Hg).

CONCLUSIONS

Gender significantly influences the evolution of the early response to pressure overload, including the transition to heart failure in rats with aortic stenosis.

Prolonged exercise alters cardiac chronotropic responsiveness in endurance athletes

OBJECTIVE

To determine whether exhaustive exercise alters cardiac adrenergic chronotropic responsiveness in endurance-trained athletes.

METHODS

Fifteen athletes were studied prospectively 2-4 days before and within 3.3 hours after completing the Hawaii Ironman Triathlon (3.9 km swim, 180.2 km bike, 24.2 km run). Increasing intravenous boluses of isoproterenol were given until the rise in heart rate was > 30 bpm (n = 3-6 doses). A log dose heart rate response curve was constructed, and the dose required to increase heart rate by 15 and 25 bpm estimated. Left ventricular size and function were also assessed by echocardiography.

RESULTS

After race finish, left ventricular volume (98 vs 83 cc), ejection fraction (56 vs 46%) and diastolic filling (3.86 vs 3.12 edv/sec) were reduced (all p < 0.01). Resting heart rate rose from 54 +/- 7 bpm to 70 +/- 10 bpm. The isoproterenol dose required to increase heart rate by 15 bpm rose from 0.6 to 1.7 micrograms by 25 bpm rose from 1.8 to 4.0 micrograms, both p < 0.01. The linear relationship between change in heart rate and log isoproterenol dose was preserved.

CONCLUSIONS

Cardiac chronotropic responsiveness is reduced following an Ironman triathlon.