scholarly journals Laser microbeam study of a rotary motor in termite flagellates. Evidence that the axostyle complex generates torque.

1978 ◽  
Vol 78 (1) ◽  
pp. 76-92 ◽  
Author(s):  
S L Tamm
Keyword(s):  
Dynamic Properties ◽  
Anterior Part ◽  
Anterior Segment ◽  
Rotation Velocity ◽  
Posterior Segment ◽  
Velocity Data ◽  
Middle Segment ◽  
Laser Microbeam ◽  
Free Running ◽  
Rotary Motor

A rotary motor in a termite flagellate continually turns the anterior part of the cell (head) in a clockwise direction. Previous descriptive observations implicated the noncontractile axostyle, which runs through the cell like a drive shaft, in the motile mechanism. This study demonstrates directly that the axostyle complex generates torque, and describes serval of its dynamic properties. By laser microbeam irradiation, the axostyle is broken into an anterior segment attached to the cell's head, and a posterior segment which projects caudally as a thin spike, or axostylar projection. Before lasing, both head and axostylar projection rotate at the same speed. After breaking the axostyle, the rotation velocity of the head decreases, depending on the length of the anterior segment. Head speed is not a linear function of axostyle length, however. In contrast, the rotation velocity of the axostylar projection always increases about 1.5 times after lasing, regardless of the length of the posterior segment. Turning the head is thus a load on the axostylar rotary motor, but the speed of the posterior segment represents the free-running motor. A third, middle segment of the axostyle, not connected to the head or axostylar projection, can also rotate independently. No ultrastructural differences were found along the length of the axostyle complex, except at the very anterior end; lenth-velocity data suggest that this region may not be able to generate torque. An electric model of the axostylar rotary motor is presented to help understand the length-velocity data.

Ocular manifestations in patients who underwent COVID-19 in the early stages after Phaco surgery with implantation of IOL

2021 ◽  
pp. 80-85
Author(s):  
T.N. Savranova ◽  
◽  
V.U. Rozukulov ◽  
A.F. Yusupov ◽  
◽  
...  
Keyword(s):  
Dry Eye ◽  
Anterior Part ◽  
Anterior Segment ◽  
Early Postoperative Period ◽  
Posterior Segment ◽  
Vascular Pathology ◽  
Ocular Manifestations ◽  
Uveal Tract ◽  
Ocular Symptoms ◽  
Rehabilitation Period

Purpose. To study the ocular manifestations in patients with pseudophakia who underwent COVID-19 during the rehabilitation period after surgery. Material and methods. 46 patients with Phaco with implantation of IOL who underwent COVID-19 in the period from 1 week to 2 months after surgery. Of the examined patients, there were 28 men (61%), 18 women (391%). The average age of the patients was 63±1,2 years. Results. In 78% of cases, vascular pathology of the anterior and posterior segments of the eyeball was observed in patients who underwent COVID-19 in the early postoperative period after Phaco with implantation of IOL. Conclusions. The main ocular symptoms from the anterior segment of the eyeball in patients in 17% of cases were the occurrence or intensification of previously existing manifestations of the «dry eye» syndrome, as well as inflammatory phenomena from the anterior part of the uveal tract. From the posterior segment of the eye, in 70% of cases, there was a progression of vascular disorders, as well as the appearance of complications associated with manifestations of hypercoagulation syndrome and systemic vasculopathy. Key words: Covid-19, cataract phacoemulsification, pseudophakia.

Studies on the Nutrition of Blow-Fly Larvae

1931 ◽  
Vol 8 (2) ◽  
pp. 109-123 ◽  
Author(s):  
R. P. HOBSON
Keyword(s):  
Proteolytic Enzymes ◽  
Anterior Segment ◽  
Posterior Segment ◽  
Ion Concentration ◽  
Gut Contents ◽  
Middle Segment ◽  
Hydrogen Ion Concentration ◽  
Alkaline Reaction ◽  
Bacterial Action ◽  
Hind Gut

1. The mid-gut in Lucilia larvae can be divided into three distinct regions (termed anterior, middle and posterior segments). 2. Histologically the anterior and posterior segments are similar. In a feeding larva the cells are highly vacuolated and contain fat; in a starved larva the cells are deeply staining and non-vacuolated. In the middle segment the cells are always deeply staining and free from vacuoles and fat, whatever the state of nutrition. 3. The hydrogen-ion concentration varies along the gut and with the nature of the food. With liquefied meat as food, the pH is 7.5-8.0 in the crop, 7.5 in the anterior segment, 3.0-3.5 in the middle segment, 7.5-8.3 in the posterior segment, and 8.0-8.5 in the hind-gut. With fresh gelatine (pH 7.0) as food, the values are the same except in the crop and anterior segment, for which the figures are respectively pH 7.0 and 6.5. 4. It has been suggested that the acidity in the middle segment may be due to an acid secretion, the most likely component being phosphoric acid. The alkaline reaction in other parts of the gut is probably caused by ammonia, which is present in the gut-contents and excreta. 5. Tryptase, peptidase and lipase are present in the mid-gut, the enzymes being concentrated in the anterior and posterior segments. The proteolytic enzymes persist in the excreta and some extra-intestinal digestion, therefore, can occur without the aid of micro-organisms. Carbohydrate-splitting enzymes are absent except for a feeble secretion of amylase in the salivary gland. 6. By combining the evidence from various sources, I have attempted to obtain a complete picture of the process of digestion, which I suggest is as follows: The food is stored unchanged in the crop and, passing into the mid-gut, is rapidly forced into the middle segment. Some absorption of water and simple products of bacterial action occurs along the anterior segment, the concentration of the food being completed in the middle segment where the acidity prevents digestion. The food, by now of a pasty constituency, passes into the posterior segment, dissolves in the alkaline fluid and is digested and absorbed. The digestive enzymes are secreted in the anterior and posterior segments, but digestion does not progress far in the anterior segment owing to the rapid passage of the food.

Digestion in the Tsetse-Fly: A Study of Structure and Function

Parasitology ◽  
1929 ◽  
Vol 21 (3) ◽  
pp. 288-321 ◽  
Author(s):  
V. B. Wigglesworth
Keyword(s):  
Epithelial Cells ◽  
Salivary Glands ◽  
Digestive Enzymes ◽  
Anterior Segment ◽  
Posterior Segment ◽  
Tsetse Fly ◽  
Peritrophic Membrane ◽  
Middle Segment ◽  
Columnar Cells ◽  
Blood Pigment

The anatomy, histology and digestive enzymes of the mid-intestine of the tsetse-fly have been investigated, and an attempt has been made to determine the functions of the various parts and to observe the changes to which they are subject during the digestion of blood.Histologically the mid-gut of Glossina consists of three regions:(i) An anterior segment of small, pale-staining, irregularly columnar cells, which comprises about half the total length of the mid-gut. The zone of giantcells containing bacteroids, which is very limited in extent, lies at about the middle of this region.(ii) A middle segment of large, deeply staining cells, heaped together in the resting state, which is separated abruptly from the anterior segment.(iii) A posterior segment, arising by gradual transition from the middle segment, composed of regular columnar cells.After a meal the blood is concentrated by the removal of fluid in the anterior segment but it shows no other change in this region. The giant-cells are greatly flattened but they do not regularly discharge the bacteroids which they contain and there is no evidence that these organisms play any part in the digestion of blood. Their possible function has been discussed.During digestion the cells in the middle segment contain globules of secretion, and vacuolated buds of cytoplasm are set free and disintegrate in the lumen. The blood shows an abrupt change on reaching this region; it turns black where it is in contact with the epithelium and amorphous masses of altered blood pigment are deposited.In the posterior segment, the epithelial cells become greatly vacuolated later in digestion and are probably concerned chiefly in absorption.The distribution of digestive enzymes agrees with these histological observations. The salivary glands and proventriculus contain no digestive enzymes, and the anterior and posterior segments of the mid-gut also are practically inactive. But the middle segment produces a very active tryptase which agrees in its pH-activity curve and other properties with the tryptase of the cockroach. A peptidase also is present but, except for a very weak amylase, enzymes acting upon carbohydrates are absent. The contents of the mid-gut are always slightly acid (about pH 6·5) and the tryptase present is well adapted to work at this reaction.These findings have been contrasted with those in a non-blood-sucking muscid (Calliphora). Here the salivary glands secrete an active amylase and the mid-gut is rich in amylase, invertase and maltase, whereas the proteolytic enzymes are extremely weak.Some observations have been made upon the tracheal supply to the walls of the gut. The epithelial cells of the middle segment have been shown to contain a very rich supply of intracellular tracheoles. These are usually difficult to make out in the resting cells but after a large meal the surface of the cells is ruptured and blood pigment enters the tracheoles and may extend to the sub-epithelial tracheoles and tracheae or even to quite large tracheal trunks. As the epithelial cells are flattened by the pressure of the meal, this pigment is set free in the lumen in the form of dark rods of haematin, which often bear a superficial resemblance to bacteria. The pigment in the deeper tubes appears to be slowly absorbed later. Intracellular tracheoles similar to these are present also in the mid-gut of Calliphora.The proventriculus in Glossina is a complex and has always been a puzzling structure. It has been shown that it acts as a sphincter between the fore-gut and mid-gut and that it is responsible for the production of the peritrophic membrane. This membrane, which is composed of chitin but contains a small quantity of protein, is secreted in the form of a fluid by the ring of large epithelial cells at the base of the proventriculus. The fluid is pressed and condensed to form a uniform membrane by being drawn through the cleft between the wall of the proventriculus and the funnel-shaped invagination of the fore-gut.The function of the peritrophic membrane has been discussed and it has been shown that it is freely permeable to digestive enzymes and to haemoglobin.

scholarly journals Posterior segment involvelent in remote lightning strike

2016 ◽  
Vol 15 (1) ◽  
pp. 40-42
Author(s):  
Atul Kumar Singh
Keyword(s):  
Retinal Detachment ◽  
Macular Oedema ◽  
Cranial Nerve ◽  
Anterior Segment ◽  
Posterior Segment ◽  
Lightning Strike ◽  
Retinal Haemorrhage ◽  
Cranial Nerve Palsies ◽  
Retinal Oedema ◽  
Multiple Cranial Nerve

Some form of ophthalmic injury is seen in the majority of lightening victims. These may be anterior segment involvement, mostly the cornea. Other lesion on the anterior segment include uveitis, hyphaema, cataract and dislocated lens. Posterior segment lesion include vitreous haemorrhage, retinal oedema, retinal haemorrhage, retinal detachment, cystoids macular oedema, chorioretinalrupture, maculopathy, CRVO and CRAO. Neuro-ophthalmic lesion include loss of pupillaryreflex, anisocoria, horner syndrome, multiple cranial nerve palsies and nystagmus.

scholarly journals COVID-19 Recombinant mRNA Vaccines and Serious Ocular Inflammatory Side Effects: Real or Coincidence?

2021 ◽  
Author(s):  
Arash Maleki ◽  
Sydney Look-Why ◽  
Ambika Manhapra ◽  
Charles Stephen Foster
Keyword(s):  
Inflammatory Diseases ◽  
Case Reports ◽  
Anterior Segment ◽  
Posterior Segment ◽  
Ischemic Optic Neuropathy ◽  
Temporal Artery Biopsy ◽  
Dexamethasone Implant ◽  
Intravitreal Dexamethasone Implant ◽  
The Right ◽  
Intravitreal Dexamethasone

Purpose: To report two cases; bilateral arteritic anterior ischemic optic neuropathy (AAION) and bilateral acute zonal occult outer retinopathy (AZOOR) after COVID-19 mRNA vaccination. Case Reports: The first patient was a 79-year-old female was presented to us 35 days after a sudden bilateral loss of vision, which occurred two days after receiving the second recombinant mRNA vaccine (Pfizer) injection. Temporal artery biopsy was compatible with AAION. At presentation, the best-corrected visual acuity was 20/1250 and 20/40 in the right and left eyes on the Snellen acuity chart, respectively. There was 3+ afferent pupillary defect in the right eye. The anterior segment and posterior segment exams were normal except for pallor of the optic nerve head in both eyes. Intraocular pressure was normal in both eyes. She was diagnosed with bilateral AAION and Subcutaneous tocilizumab 162 mg weekly was recommended with monitoring her ESR, CRP, and IL-6. The second patient was a 33-year-old healthy female who was referred to us for a progressive nasal field defect in her left eye, and for flashes in both eyes. Her symptoms started 10 days after receiving the second recombinant mRNA vaccine (Moderna) injection. Complete bloodwork performed by a uveitis specialist demonstrated high ESR (25) and CRP (19) levels. As a result, she was diagnosed with unilateral AZOOR in her left eye and was subsequently treated with an intravitreal dexamethasone implant in the same eye. At presentation, vision was20/20 in both eyes. The anterior segment and posterior segment exams were completely normal except for the presence of abnormal white reflex in the temporal macula of her left eye. We diagnosed her with bilateral AZOOR. Since she was nursing, intravitreal dexamethasone implant was recommended for the right eye. Conclusion: There may be a correlation between ocular inflammatory diseases with autoimmune mechanism and the mRNA COVID-19 vaccination.

scholarly journals Complete reconstruction of anterior segment surgery for a patient with traumatic cataract and iris defects: a case report

2019 ◽  
Author(s):  
Zhenyu Wang ◽  
Xuemin Li
Keyword(s):  
Ocular Trauma ◽  
Anterior Segment ◽  
Posterior Segment ◽  
Traumatic Cataract ◽  
Case Presentation ◽  
Iris Defect ◽  
Uncorrected Visual Acuity ◽  
Posterior Synechia ◽  
Anterior Segment Surgery

Abstract Background: Ocular trauma has relationship with variable damage towards anterior segment or posterior segment. Among them, cornea, iris and lens are vulnerable to injury. For patients with traumatic cataract and other anterior segment trauma， complete reconstruction of anterior segment surgery can be a good option to restore patients’ anterior segment that helps them regain their vision. Case presentation: We presented a case of traumatic cataract with iris defects after explosive trauma. A surgery was done to fully reconstruct the anterior segment of the patient’s left eye including separating posterior synechia of iris, removing cataract and implantation of IOL. Postoperatively, the patient didn’t complain about photophobia anymore and the uncorrected visual acuity (UCVA) of the patient reached from counting fingers to 20/25 and remained stable on follow-up at 1 week and 1 month. Conclusion: Our case suggested the importance of completely reconstruct anterior segment for patients who have traumatic cataract with traumatic iris defects and its benefits for society. Keywords: Traumatic cataract; Traumatic iris defect; Surgery

Investigations and their interpretation

2018 ◽  
pp. 51-108
Keyword(s):  
Blood Flow ◽  
Visual Field ◽  
Adaptive Optics ◽  
Anterior Segment ◽  
Field Testing ◽  
Posterior Segment ◽  
Flow Quantification ◽  
Blood Flow Quantification ◽  
Clinical Strategies ◽  
Goldmann Perimetry

‘Investigations and their interpretation’ introduces the reader to both standard and emerging technologies that enable assessment of the structure or function of the eye and visual system. Starting with visual field testing, the chapter covers automated and Goldmann perimetry, novel protocols and progression analysis. Anterior segment imaging covers keratometry, topography and OCT. Posterior segment imaging includes angiographic techniques, novel blood flow quantification methods, OCT, and adaptive optics. Electrodiagnostic tests are introduced including multifocal techniques. Finally ophthalmic ultrasonography and radiology are supported by clinical strategies and examples to support the practice and interpretation of these techniques.

scholarly journals Imaging depth extension of optical coherence tomography in rabbit eyes using optical clearing agents

2020 ◽  
Vol 245 (18) ◽  
pp. 1629-1636
Author(s):  
Ruiming Kong ◽  
Wenjuan Wu ◽  
Rui Qiu ◽  
Lei Gao ◽  
Fengxian Du ◽  
...  
Keyword(s):  
Optical Coherence Tomography ◽  
Ex Vivo ◽  
Light Attenuation ◽  
Anterior Segment ◽  
Posterior Segment ◽  
Glycerol Solution ◽  
Optical Coherence ◽  
Optical Clearing ◽  
Imaging Depth

Optical coherence tomography has become an indispensable diagnostic tool in ophthalmology for imaging the retina and the anterior segment of the eye. However, the imaging depth of optical coherence tomography is limited by light attenuation in tissues due to optical scattering and absorption. In this study of rabbit eye both ex vivo and in vivo, optical coherence tomography imaging depth of the anterior and posterior segments of the eye was extended by using optical clearing agents to reduce multiple scattering. The sclera, the iris, and the ciliary body were clearly visualized by direct application of glycerol at an incision on the conjunctiva, and the posterior boundary of sclera and even the deeper tissues were detected by submerging the posterior segment of eye in glycerol solution ex vivo or by retro-bulbar injection of glycerol in vivo. The ex vivo rabbit eyes recovered to their original state in 60 s after saline-wash treatment, and normal optical coherence tomography images of the posterior segment of the sample eyes proved the self-recovery of in vivo performance. Signal intensities of optical coherence tomography images obtained before and after glycerol treatment were compared to analysis of the effect of optical clearing. To the best of our knowledge, this is the first study for imaging depth extension of optical coherence tomography in both the anterior and posterior segments of eye by using optical clearing agents.

scholarly journals Open-Globe Injury With Intraocular Foreign Body

2020 ◽  
pp. 247412642096503
Author(s):  
Filippos Vingopoulos ◽  
Yvonne Wang ◽  
Seanna Grob ◽  
Chloe Yang Ling Li ◽  
Dean Eliott ◽  
...  
Keyword(s):  
Foreign Body ◽  
Primary Repair ◽  
Anterior Segment ◽  
Case Series ◽  
Visual Outcome ◽  
Posterior Segment ◽  
Open Globe ◽  
Time From Injury

Purpose: To investigate characteristics of Open Globe Injuries (OGI) that presented with Intra-Ocular Foreign Body (IOFB), along with their long-term visual outcomes and complications. Methods: Retrospective interventional consecutive case series of OGIs with IOFBs that presented at Massachusetts Eye and Ear from 2010 to 2015. Data collected included time from injury to OGI repair, location of IOFB, retinal detachment (RD) rate, presenting and final visual acuity and subsequent surgeries. Results: Fifty-seven consecutive cases of OGIs with IOFBs were included. Mean follow-up was 28 months and median time from injury to OGI repair was 0 days. Overall, 38/57 (66.7%) eyes achieved final vision of 20/40 or better and 43/57 (75.4%) 20/150 or better. Thirty-three cases had IOFBs in the anterior segment only, 24 cases had posterior segment involvement. Thirty percent of cases (17/57) were complicated by an RD, 58.3% (14/24) in the posterior versus 9.1% (3/33) in the anterior IOFB group ( P = .01). There were no cases of endophthalmitis. Posterior IOFB and higher zone of injury were risk factors for RD both at presentation (both P < .001) and post-primary repair (both P < .001). Posterior IOFB was associated with higher vitrectomy rates both at presentation ( P < .001) and post-primary repair ( P = .002) and worse long-term visual outcome ( P = .01). Conclusions: OGIs with IOFB involving the posterior segment are associated with higher complication and re-operation rates and worse visual prognosis compared to those involving the anterior segment only.

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