The user experience design of a novel microscope within SurgiSim, a virtual reality surgical simulator

PURPOSE

Virtual reality (VR) simulation has the potential to advance surgical education, procedural planning, and intraoperative guidance. "SurgiSim" is a VR platform developed for the rehearsal of complex procedures using patient-specific anatomy, high-fidelity stereoscopic graphics, and haptic feedback. SurgiSim is the first VR simulator to include a virtual operating room microscope. We describe the process of designing and refining the VR microscope user experience (UX) and user interaction (UI) to optimize surgical rehearsal and education.

METHODS

Human-centered VR design principles were applied in the design of the SurgiSim microscope to optimize the user's sense of presence. Throughout the UX's development, the team of developers met regularly with surgeons to gather end-user feedback. Supplemental testing was performed on four participants.

RESULTS

Through observation and participant feedback, we made iterative design upgrades to the SurgiSim platform. We identified the following key characteristics of the VR microscope UI: overall appearance, hand controller interface, and microscope movement.

CONCLUSION

Our design process identified challenges arising from the disparity between VR and physical environments that pertain to microscope education and deployment. These roadblocks were addressed using creative solutions. Future studies will investigate the efficacy of VR surgical microscope training on real-world microscope skills as assessed by validated performance metrics.

Pilot Study of Optical Topographic Imaging Based Neuronavigation for Mastoidectomy

BACKGROUND

Mastoidectomy involves drilling the temporal bone while avoiding the facial nerve, semicircular canals, sigmoid sinus, and tegmen. Optical topographic imaging (OTI) is a novel registration technique that allows rapid registration with minimal navigational error. To date, no studies have examined the use of OTI in skull-base procedures.

METHODS

In this cadaveric study, 8 mastoidectomies were performed in 2 groups-4 free-hand (FH) and 4 OTI-assisted mastoidectomies. Registration accuracy for OTI navigation was quantified with root mean square (RMS) and target registration error (TRE). Procedural time, percent of mastoid resected, and the proximity of the mastoidectomy cavity to critical structures were determined.

RESULTS

The average RMS and TRE associated with OTI-based registration were 1.44 mm (±0.83 mm) and 2.17 mm (±0.89 mm), respectively. The volume removed, expressed as a percentage of the total mastoid volume, was 37.5% (±10.2%) versus 31.2% (±2.3%), P = 0.31, for FH and OTI-assisted mastoidectomy. There were no statistically significant differences between FH and OTI-assisted mastoidectomies with respect to proximity to critical structures or procedural time.

CONCLUSIONS

This work is the first examining the application of OTI neuronavigation in lateral skull-base procedures. This pilot study revealed the RMS and TRE for OTI-based navigation in the lateral skull base are 1.44 mm (±0.83 mm) and 2.17 mm (±0.89 mm), respectively. This pilot study demonstrates that an OTI-based system is sufficiently accurate and may address barriers to widespread adoption of navigation for lateral skull-base procedures.

Predictive Ability of Direct Electrical Stimulation on Facial Nerve Function Following Vestibular Schwannoma Surgery: A Systematic Review and Meta-analysis

OBJECTIVE

Facial nerve preservation is critical in vestibular schwannoma (VS) surgery. Direct electrical stimulation (DES) is a widely used method for intraoperative localization of the facial nerve and assessment of nerve integrity. We sought to assess the predictive ability of DES parameters on facial nerve function post-VS surgery.

DATABASES REVIEWED

A systematic literature search of English-language studies published from 1946 to 2019 was undertaken using EMBASE, MedLine/PubMed, and the Cochrane Central Register of Controlled Trials.

METHODS

Included studies involved patients undergoing VS surgery and assessed predictive ability of any DES parameter on postoperative facial function. Two authors independently reviewed studies and extracted data. Meta-analysis of diagnostic accuracy of DES parameters was used to calculate pooled sensitivities and specificities of common cutoffs. For DES parameters reported by less than four studies, outcomes were reported descriptively.

RESULTS

A MST cutoff of 0.10 mA had sensitivity of 0.76 (95% CI 0.53-0.90) and specificity 0.68 (95% CI 0.42-0.87) for facial function in the long term, and MST 0.05 mA had sensitivity 0.73 (95% CI 0.58-0.84) and specificity 0.74 (95% CI 0.59-0.85). CMAP amplitude < 500 μV had sensitivity of 0.87 (95% CI 0.78-0.93) for poor short-term facial function.

CONCLUSIONS

A CMAP amplitude response < 500 μV is sensitive for poor short-term facial function, whereas MST values of 0.05 mA and 0.10 mA are both sensitive and specific in the long term. Other DES parameters may be able to accurately predict both short- and long-term postoperative facial function, but have been less studied.

An operative barrier system for skull base and mastoid surgery: creating a safe operative theatre in the era of COVID-19

Within Neurotology, special draping systems have been devised for mastoid surgery recognizing that drilling of middle ear mucosa is an aerosol generating medical procedure (AGMP) which can place surgical teams at risk of COVID-19 infection. We provide a thorough description of a barrier system utilized in our practice, along with work completed by our group to better quantify its effectiveness. Utilization of a barrier system can provide near complete bone dust and droplet containment within the surgical field and prevent contamination of other healthcare workers. As this is an early system, further adaptations and national collaborations are required to ultimately arrive at a system that seamlessly integrates into the surgical suite. While these barrier systems are new, they are timely as we face a pandemic, and can play a crucial role in safely resuming surgery.

Waste and recycling among orthopedic subspecialties

Background

It is estimated that one-quarter to half of all hospital waste is produced in the operating room. Recycling of surgical waste in the perioperative setting is uncommon, even though there are many recyclable materials. The objective of this study was to determine the amount of waste produced in the preoperative and operative periods for several orthopedic subspecialties and to assess how much of this waste was recycled.

Methods

Surgical cases at 1 adult and 1 pediatric tertiary care hospital in Calgary, Alberta, were prospectively chosen from 6 orthopedic subspecialties over a 1-month period. Waste was collected, weighed and divided into recyclable and nonrecyclable categories in the preoperative period and into recyclable, nonrecyclable, linen and biological categories in the intraoperative period. Waste bags were weighed using a portable hand-held scale. The primary outcome was the amount of recyclable waste produced per case. Secondary outcomes included the amount of nonrecyclable, biological and total waste produced. An analysis of variance was performed to test for statistically significant differences among subspecialties.

Results

This study included 55 procedures. A total of 341.0 kg of waste was collected, with a mean mass of 6.2 kg per case. Arthroplasty produced a greater amount of recyclable waste per case in the preoperative (2017.1 g) and intraoperative (938.6 g) periods as well as total recyclable waste per case, resulting in a greater ratio of waste recycling per case then nearly all other subspecialties in the preoperative (86%) and intraoperative (14%) periods. Arthroplasty similarly produced a greater amount of nonrecyclable waste per case (5823.6 g) than the other subspecialties, most of which was produced during the intraoperative period (5512.9 g). Overall an average of 27% of waste was recycled per case.

Conclusion

Among orthopedic subspecialties, arthroplasty is one of the largest waste producers and it has the highest potential for recycling of materials. Effective recycling programs in the operating room can reduce our ecological footprint by diverting waste from landfills, as our study revealed that nearly three-quarters of this waste is recyclable.

Systematic Review of the Quality of Economic Evaluations in the Otolaryngology Literature

Objective

To evaluate the quality of economic evaluations published in the otolaryngology—head and neck surgery literature, which will identify methodologic weaknesses that can be improved on in future studies. A secondary objective is to identify factors that may be associated with higher quality economic evaluations.

Data Sources

Ovid Medline (including PubMed), Embase, and the National Health Services Economic Evaluation databases.

Review Methods

A systematic search was performed of the aforementioned databases according to PRISMA guidelines. The search was performed using otolaryngology key terms combined with the term cost. A manual search of 36 otolaryngology journals was also performed. Included studies were graded using the Quality of Health Economics Studies instrument, a 16-item checklist providing a total quality score of 100.

Results

Fifty studies were identified, and the mean quality rating was 54.7/100 (SD = 30.9). The most commonly omitted methodology components were a lack of discussion of limitations and biases, failure to address the negative outcomes of examined interventions, and a lack of a robust sensitivity analysis. Higher quality economic evaluations were associated with a higher journal impact factor (correlation coefficient r = 0.62, P = .0001), having an author with a PhD in health economics ( r = 0.56, P = .0001), and having authors who have published prior economic evaluations ( r = 0.46, P = .001).

Conclusion

Results from this study have demonstrated that there are several methodological domains that can be improved on when publishing economic evaluations in the otolaryngology literature. Authors should follow recommended methodological and reporting guidelines to optimize the transparency and accuracy of the overall conclusions.

Assessment of Ondansetron-Associated Hypokalemia in Pediatric Oncology Patients

Objectives. Ondansetron is a 5-hydroxytryptamine (5-HT3, serotonin) receptor antagonist used as antiemetic prophylaxis preceding chemotherapy administration. Hypokalemia is a rare complication of ondansetron, which may be underreported due to confounding emesis and chemotherapy-induced tubulopathy. We performed a prospective cohort study to determine if ondansetron caused significant hypokalemia independently as a result of renal potassium wasting. Methods. Twelve patients were recruited, with ten completing the study. Blood and urine samples were collected before and after ondansetron administration in patients admitted for intravenous (IV) hydration and chemotherapy. Dietary histories and IV records were analyzed to calculate sodium and potassium balances. Results. We observed an expected drop in urine osmolality, an increase in urine sodium, but no statistically significant change in sodium or potassium balance before and after ondansetron. Conclusion. Ondansetron does not cause significant potassium wasting in appropriately hydrated and nutritionally replete patients. Careful monitoring of serum potassium is recommended in patients with chronic nutritional or volume status deficiencies receiving this medication.

Indicator microbes correlate with pathogenic bacteria, yeasts and helminthes in sand at a subtropical recreational beach site

AIMS

Research into the relationship between pathogens, faecal indicator microbes and environmental factors in beach sand has been limited, yet vital to the understanding of the microbial relationship between sand and the water column and to the improvement of criteria for better human health protection at beaches. The objectives of this study were to evaluate the presence and distribution of pathogens in various zones of beach sand (subtidal, intertidal and supratidal) and to assess their relationship with environmental parameters and indicator microbes at a non-point source subtropical marine beach.

METHODS AND RESULTS

In this exploratory study in subtropical Miami (Florida, USA), beach sand samples were collected and analysed over the course of 6 days for several pathogens, microbial source tracking markers and indicator microbes. An inverse correlation between moisture content and most indicator microbes was found. Significant associations were identified between some indicator microbes and pathogens (such as nematode larvae and yeasts in the genus Candida), which are from classes of microbes that are rarely evaluated in the context of recreational beach use.

CONCLUSIONS

Results indicate that indicator microbes may predict the presence of some of the pathogens, in particular helminthes, yeasts and the bacterial pathogen Staphylococcus aureus including methicillin-resistant forms. Indicator microbes may thus be useful for monitoring beach sand and water quality at non-point source beaches.

SIGNIFICANCE AND IMPACT OF THE STUDY

The presence of both indicator microbes and pathogens in beach sand provides one possible explanation for human health effects reported at non-point sources beaches.

Assessing components of the natural environment of the Upper Danube and Upper Brahmaputra river basins

Abstract. A comprehensive understanding of the interplay between the natural environment and the human dimension is one of the prerequisites to successful and sustaining IWRM practises in large river basins such as the Upper Brahmaputra river basin or the Upper Danube river basin. These interactions, their dynamics and changes, and the likely future scenarios were investigated in the BRAHMATWINN project with a series of tools from remote sensing and geoinformatics. An integrated assessment of main components of the natural environment in the two river basins as well as in five reference catchments within those basins, has led to the delineation of hydrological response units (HRUs). HRUs are spatial units bearing a uniform behaviour in terms of the hydrological response regime, as a function of physical parameters land use, soil type, water, vegetation cover and climate. Besides the delineated HRUs which are available in a spatially exhaustive manner for all reference catchments, the following information were provided as spatial layers: (1) uniform digital surface models of both the twinned basins and the reference catchments; (2) glacier areas and the magnitude of glacier loss; (3) mountain permafrost distribution and identification of areas particularly affected by permafrost thaw; (4) a consistent land use/land cover information in all reference catchments; and (5) the vulnerabilities of wetlands and groundwater in terms of anthropogenic impact and climate change.

Combined photodynamic and low-level laser therapies as an adjunct to nonsurgical treatment of chronic periodontitis

BACKGROUND AND OBJECTIVE

In recent years, there has been a growing interest in the use of dental lasers for treatment of periodontal diseases. The purpose of this short-term clinical trial was to evaluate the effects of a combination of photodynamic therapy with low-level laser therapy as an adjunct to nonsurgical treatment of chronic periodontitis.

MATERIAL AND METHODS

Twenty-four nonsmoking adults with untreated chronic periodontitis were randomly assigned in a split-mouth design to receive scaling and root debridement with or without one course of adjunctive photodynamic therapy and low-level laser therapy within 5 d. Plaque, bleeding on probing, probing depth and gingival recession were recorded at baseline, 1 and 3 mo after the treatment. Gingival crevicular fluid was collected for assay of interleukin-1β levels at baseline, 1 wk and 1 mo.

RESULTS

The test teeth achieved greater reductions in the percentage of sites with bleeding on probing and in mean probing depth at 1 mo compared with the control teeth (p < 0.05). A significant decrease in gingival crevicular fluid volume was observed in both groups at 1 wk (p < 0.001), with a further decrease at 1 mo in the test sites (p < 0.05). The test sites showed a greater reduction of interleukin-1β levels in gingival crevicular fluid at 1 wk than the control sites (p < 0.05). No significant differences in periodontal parameters were found between the test and control teeth at 3 mo.

CONCLUSIONS

The present study suggests that a combined course of photodynamic therapy with low-level laser therapy could be a beneficial adjunct to nonsurgical treatment of chronic periodontitis on a short-term basis. Further studies are required to assess the long-term effectiveness of the combination of photodynamic therapy with low-level laser therapy as an adjunct in nonsurgical treatment of periodontitis.

Carcass and meat quality traits of wild boar (Sus scrofas. L.) with 2n=36 karyotype compared to those of phenotypically similar crossbreeds (2n=37 and 2n=38) raised under same farming conditions. 1. Carcass quantity and meat dressing

The aim of this study was to compare wild boar (chromosomal number 2n=36) to phenotypically similar animals of 2n=37 and 2n=38 chromosomes (crossbreeds) with respect to live weight, carcass yield, meat yield, fat and weight of inner organs. All animals were born and raised on the same farm and slaughtered at 39 weeks. The final live weight of wild boar 2n=36 was significantly lower (47.2kg) as compared to crossbreeds (80.0kg). Animals 2n=36 had more carcass yields (65.5%) than 2n=37 karyotype (64.9%) and 2n=38 (64.4%). Wild boar had the highest yields for the cuts with bones and boneless cuts compared to crossbreeds. Therefore, variations in karyotype are accompanied by differences in some carcass quantitative traits, i.e., 2n=36 grow and fatten slower than crossbreeds 2n=37 and 2n=38.

Rosai-Dorfman disease of the testis: an unusual entity that mimics testicular malignancy

A 47 year old Chinese man with diabetes mellitus and previously treated pulmonary tuberculosis presented with painless right testicular enlargement of 1 month's duration. He underwent an orchidectomy for presumed testicular neoplasm corroborated clinicoradiologically. Histological examination of the testicular mass revealed an inflammatory lesion comprising lymphocytes, plasma cells and sheets of pale staining histiocytes, some containing lymphocytes within their ample cytoplasm, suggestive of emperipolesis. S100 immunohistochemistry stained the histiocytes, while ultrastructural examination confirmed emperipolesis. A diagnosis of Rosai-Dorfman disease was made, an exceedingly rare testicular lesion. Clinicoradiological findings mimicked a neoplasm, while the inflammatory histological appearances with occasionally discerned multinucleated cells raised the possibility of xanthogranulomatous orchitis. Tuberculous orchitis was excluded through negative Ziehl-Neelsen stains and PCR for mycobacterium, while seminoma, which sometimes features a predominant inflammatory component obscuring neoplastic cells, was excluded by absent immunostaining for placental alkaline phosphatase and CD117.

The effect of bi-level positive airway pressure on postoperative pulmonary function following gastric surgery for obesity

The severely obese patient has varying degrees of intrinsic reduction of expiratory flow rates and lung volumes. Thus, the severely obese patient is predisposed to postoperative atelectasis, ineffective clearing of respiratory secretions, and other pulmonary complications. This study evaluated the effect of bi-level positive airway pressure (BiPAP) on pulmonary function in obese patients following open gastric bypass surgery Patients with a body mass index (BMI) of at least 40 kg/m2 who were undergoing elective gastric bypass were eligible to be randomized to receive either BiPAP during the first 24 h postoperatively or conventional postoperative care. Patients with significant cardiovascular and pulmonary diseases were excluded from the study. Forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1.0), peak expiratory flow rate (PEFR), and percent hemoglobin oxygen saturation (SpO2) were measured preoperatively, and on postoperative days 1, 2, and 3. Twenty-seven patients were entered in the study 14 received BiPAP and 13 received conventional postoperative care. There was no significant difference preoperatively between the study and control groups in regards to age, BMI, FVC, FEV1.0, PEFR or SpO2. Postoperatively expiratory flow was decreased in both groups. However, the FVC and FEV1.0 were significantly higher on each of the three consecutive postoperative days in the patients who received BiPAP therapy. The SpO2 was significantly decreased in the control group over the same time period. Prophylactic BiPAP during the first 12-24 h postoperatively resulted in significantly higher measures of pulmonary function in severely obese patients who had undergone elective gastric bypass surgery. These improved measures of pulmonary function, however, did not translate into fewer hospital days or a lower complication rate in our study population of otherwise healthy obese patients. Further study is necessary to determine if BiPAP therapy in the first 24 postoperative hours would be of benefit in severely obese patients with comorbid illnesses who have undergone elective gastric bypass.

Acute pain services in Hong Kong: facilities, volume, and quality

Acute pain services in public hospitals in Hong Kong were studied. Audit data on the volume and quality of acute pain services were collected prospectively from 1997 to 1999, and data on related facilities were collected in 2000. About 20% of patients undergoing a major operation received an acute pain service; of these, 78.6% were satisfied with the treatment provided. In 2000, 86% (18/21) of hospitals providing anaesthetic services were running an acute pain service. Staffing was better in hospitals providing a high volume of acute pain services, ranging from a full-time specialist anaesthesiologist assisted by a half-time trainee to a half-time specialist assisted by a full- or half-time trainee. However, only four hospitals were staffed with pain nurses. In total, 57% of patients received intravenous patient-controlled analgesia and 32% epidural analgesia. The mean duration of acute pain service treatment was 3.1 days. Currently anaesthesiologist-based acute pain services take care of a limited number of patients. To expand the coverage, there should be a move towards an anaesthesiologist-led, pain nurse-based, acute pain service. The present shortage of pain nurses should be addressed.

Anaesthetic clinical indicators in public hospitals providing anaesthetic care in Hong Kong: prospective study

OBJECTIVES

To assess the quality of anaesthetic services as defined in the six anaesthetic clinical indicators against preset standards and to identify risk factors for adverse events in the recovery room.

DESIGN

Prospective study.

SETTING

All public hospitals providing anaesthetic care in Hong Kong.

PATIENTS

Eighteen thousand, seven hundred and fifty-nine patients receiving elective or emergency anaesthesia administered by anaesthetists from June 1998 to July 1998.

MAIN OUTCOME MEASURES

Patient demographics, American Society of Anesthesiologists status, category and nature of operation, presence of preoperative anaesthetic visit in ward, type of anaesthesia, reasons for a recovery room stay of more than a 2-hour duration, intubation to relieve respiratory distress in the recovery room, presence of hypothermia in the recovery room for operations lasting more than 2 hours, and dental or ocular injuries attributable to anaesthesia.

RESULTS

There are two major findings from this study. Firstly, a high incidence of hypothermia in the recovery room was reported. Secondly, a greater risk of prolonged stay in the recovery room was identified for patients older than 65 years, major operations, and anaesthetic techniques using combined general and regional anaesthesia.

CONCLUSION

The six anaesthetic clinical indicators reflected the provision of anaesthetic care in public hospitals in Hong Kong. Good compliance to the preset standard of the anaesthetic clinical indicators was achieved during the study period.

Influence of changes in gravity on the response of lung and vascular cells to ischemia/reperfusion in vitro

Gravity and other physical forces (e.g., shear stress or mechanical stretch) will affect organ and cellular function, e.g., blood flow distribution, gas exchange, alveolar size and mechanical stresses within the lung. Microgravity produced marked alterations in lung blood flow and ventilation distribution while hypergravity exaggerated the regional differences in lung structure and function. Microgravity was found to decrease the metabolic activity in cardiac cells, WI-38 embryonic lung cells, and human lymphocytes. These studies show that changes in gravity will affect several aspects of organ and cellular function and produce major changes in blood flow and tissue/organ perfusion. However, these past studies have not addressed whether ischemia-reperfusion injury will be exacerbated or, ameliorated by changes in the gravity environment, e.g., space flight. Currently, nothing is known about how gravity will affect the susceptibility of different lung and vascular cells to this type of injury. Ischemia injury is the underlying cause of many clinical disorders with high morbidity and mortality. The subsequent reperfusion (reoxygenation) further compounds the initial ischemic stress. Understanding the possible exacerbation of transient ischemia under the stress of space flight or an increase in gravity is critical. We conducted studies that examined whether alterations in gravity affect the susceptibility of cells to ischemia-reperfusion injury, using an in vitro anoxia-reoxygenation model.

The evolution of disability care and case management: identifying core competencies

Driven by efforts to control disability costs and encouraged by legislation promoting the accommodation of workers with impairments, disability management (DM) efforts are burgeoning! As these efforts expand, increasing numbers of case managers find themselves practicing in the DM arena.

Wound healing following injury to vascular smooth muscle cell cultures is modulated by culture under hypergravity

Anticipated hazards for crewmembers in future long-term space flights may result in a variety of injuries including fractures, deep punctures or cuts. The microgravity environment of space may complicate the wound healing process. Myofibroblasts have been proposed to play a role in wound contraction; these cells develop from tissue fibroblasts sue fibroblasts develop numerous features found in vascular smooth muscle cells (SMC), ultrastructural features, expression of alpha-SM actin and microfilament bundles. These changes have been shown to be inducible by TGF beta 1. Previous studies have also shown that TGF beta 1 is capable of initiating and regulating critical events in bone fracture, soft tissue, dermal wound healing. Several studies have suggested that bFGF may also be involved in the wound healing process, and that the interactions of bFGF with TGF beta 1 control the overall repair of a wounded tissue. The formation (angiogenesis) and/or repair of blood vessels is also essential for wound healing. Both TGF beta 1 and bFGF have been shown to affect both angiogenesis and vascular injury repair. However, the response of cells following injury, in a microgravity or hypergravity (HG) environment has not been evaluated. We assessed the influence of HG (centrifugation at 6G) and clinostat rotation at 30 rpm (CR) on the response of SMC to a denudation injury. We also examined the possible involvement of c-myc, c-fos and TGF beta 1 in meeting the response of SMC to wounding.

Cloning of a cysteine protease required for the molting of Onchocerca volvulus third stage larvae

We have investigated the involvement of a cysteine protease in the development of Onchocerca volvulus fourth stage larvae (L4) by testing the effect of cysteine protease inhibitors on the survival of third stage larvae (L3), and the molting of L3 to L4 in vitro. When larvae were cultured in the presence of specific inhibitors, the peptidyl monofluoromethylketones, viability of either L3 or L4 was not affected. However, the inhibitors reduced the number of L3 that molted to L4 in vitro in a time- and dose-dependent manner. Molting was completely inhibited in the presence of 50-250 microM inhibitor. Ultrastructural examination of L3 that did not molt in the presence of inhibitors indicated that new L4 cuticle was synthesized, but there was no separation between the L3 and the L4 cuticles. The endogenous cysteine protease was detected in molting larvae after binding to labeled inhibitors, and by antibodies directed against a recombinant O. volvulus L3 cysteine protease that was cloned and expressed. The enzyme was detected in cuticle regions where the separation between the cuticles occurs in molting larvae. These studies suggest that molting and successful development of L4 depends on the expression and release of a cysteine protease.

[99mTc-MIBI used for diagnosis of portal hypertension: an experimental study]

The authors investigated the relationship between portal-systemic shunting and portal pressure in 16 CCl4-induced cirrhotic wistar rats by 99mTc-MIBI photography of heart and liver. Based on radio-counts taken at 30 minutes after 99mTc-MIBI was given per rectum 8 rats or medial clonic vein 8 rats, heart radio-counts/liver radio-counts (H/L) and portal-systemic shunting index (SI) were recorded. It was shown that 1. H/L and SI of the two cirrhotic groups were greater than those of normals (P < 0.001); 2. H/L in cirrhotic rats by rectum 99mTc-MIBI administration was more closely related to free portal pressure (FPP, r = 0.83, P < 0.01) than in those by venous route (r = 0.74, P < 0.05) and its regressive formation FPP (kPa) = 0. 24 + 4.06 (H/L) was deduced and used to calculate portal pressure of cirrhotic rats. The very good relationship between the calculated and measured portal venous pressure was shown in a group of 12 cirrhotic rats (r = 0.85, P < 0.01). These findings suggested that the rectum administration of 99mTc-MIBI may be a useful method in calculating portal pressure and portal-systemic shunting in portal hypertensive patients.

The Caulobacter crescentus flaFG region regulates synthesis and assembly of flagellin proteins encoded by two genetically unlinked gene clusters

At a specific time in the Caulobacter crescentus cell cycle, a single flagellar filament and multiple receptor sites for the swarmer-specific phage phi Cbk are assembled at one pole of the predivisional cell. One cluster of genes required for this morphogenesis, the flaYG region, includes the flgJKL genes, which encode structural proteins of the flagellar filament. These flagellin genes are flanked by genes required for filament assembly, the flaYE genes at one end and the flaF-flbT-flbA-flaG genes at the other. In this study, we characterized mutants carrying large chromosomal deletions within this region. Several of these strains are phi CbK resistant and produce a novel 22-kDa flagellin that is not assembled into flagella. Merodiploid strains containing either the entire flaFG region or individual fla transcription units from this region were constructed. These strains were used to correlate the presence or absence of specific gene products to changes in flagellin synthesis, filament assembly, or phage sensitivity. As a result of these studies, we were able to conclude that (i) the production of the 22-kDa flagellin results from the absence of the flbA and flaG gene products, which appear to be components of a flagellin-processing pathway common to the 25-, 27-, and 29-kDa flagellins; (ii) flbT negatively modulates the synthesis of the 27- and 25-kDa flagellins from two genetically unlinked gene clusters; (iii) flgL is the only flagellin gene able to encode the 27-kDa flagellin, and this flagellin appears to be required for the efficient assembly of the 25-kDa flagellins; (iv) flaF is required for filament assembly; and (v) phi CbK resistance results from the deletion of at least two genes in the flaFG region.

Caldesmon and the structure of smooth muscle thin filaments: immunolocalization of caldesmon on thin filaments

Antibodies reacting with chicken gizzard caldesmon were used to determine the distribution of caldesmon on smooth muscle thin filaments. Antibodies developed against both the intact caldesmon molecule and a 40 kilodalton proteolytic fragment cause thin filaments to aggregate laterally. Aggregates produced with the latter antibody display regular periodic labelling with a repeat of approximately 38 nm, a distribution characteristic of proteins associated with tropomyosin on thin filaments. The stoichiometry of caldesmon on thin filaments has been critically reevaluated and alternative models of caldesmon distribution on thin filaments are proposed.

Microvascular rarefaction and tissue vascular resistance in hypertension

The purpose of this study was to quantitatively estimate the relative contribution of arteriolar rarefaction (disappearance of microvessels) and arteriolar constriction to the increases in total peripheral resistance and changes in the patterns of flow distribution observed in hypertension. A mathematical model of the hamster cheek pouch intraluminal microcirculation was constructed based on data from the literature and observations from our own laboratory. Separate rarefaction and constriction of third-order (3A) and fourth-order (4A) arterioles were performed on the model, and the results were quantified based on the changes of the computed vascular resistance. The degree of increase in resistance depended both on the number and the order of vessels rarefied or constricted and also on the position of those vessels in the network. The maximum increases in resistance obtained in the model runs were 21% for rarefaction and 75% for constriction. Rarefaction, but not constriction, produced large increases in the degree of heterogeneity of blood flow in the various vessel orders. These results demonstrate that vessel rarefaction significantly influences tissue blood flow resistance to a degree comparable with vessel constriction; however, unlike constriction, microvascular rarefaction markedly altered blood flow distribution in our model of the hamster cheek pouch vascular bed. These findings conform with the hypothesis that a significant component of the increase in total peripheral resistance in hypertension may be due to vessel rarefaction.