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Biomedical subjects

M Maus

Publications and source records attributed to M Maus.

At least 19 recordsLinked to original sources
PubMed2006

2-Deoxyglucose and NMDA inhibit protein synthesis in neurons and regulate phosphorylation of elongation factor-2 by distinct mechanisms.

Cerebral ischaemia is associated with brain damage and inhibition of neuronal protein synthesis. A deficit in neuronal metabolism and altered excitatory amino acid release may both contribute to those phenomena. In the present study, we demonstrate that both NMDA and metabolic impairment by 2-deoxyglucose or inhibitors of mitochondrial respiration inhibit protein synthesis in cortical neurons through the phosphorylation of eukaryotic elongation factor (eEF-2), without any change in phosphorylation of initiation factor eIF-2alpha. eEF-2 kinase may be activated both by Ca(2+)-independent AMP kinase or by an increase in cytosolic Ca2+. Although NMDA decreases ATP levels in neurons, only the effects of 2-deoxyglucose on protein synthesis and phosphorylation of elongation factor eEF-2 were reversed by Na(+) pyruvate. Protein synthesis inhibition by 2-deoxyglucose was not as a result of a secondary release of glutamate from cortical neurons as it was not prevented by the NMDA receptor antagonist 5-methyl-10,11-dihydro-5H-dibenzo-(a,d)-cyclohepten-5,10-imine hydrogen maleate (MK 801), nor to an increase in cytosolic-free Ca2+. Conversely, 2-deoxyglucose likely activates eEF-2 kinase through a process involving phosphorylation by AMP kinase. In conclusion, we provide evidence that protein synthesis can be inhibited by NMDA and metabolic deprivation by two distinct mechanisms involving, respectively, Ca(2+)-dependent and Ca(2+)-independent eEF-2 phosphorylation.

Animals↗
PubMed2001

Triplet states as non-radiative traps in multichromophoric entities: single molecule spectroscopy of an artificial and natural antenna system.

Energy transfer in antenna systems, ordered arrays of chromophores, is one of the key steps in the photosynthetic process. The photophysical processes taking place in such multichromophoric systems, even at the single molecule level, are complicated and not yet fully understood. Instead of directly studying individual antenna systems, we have chosen to focus first on systems for which the amount of chromophores and the interactions among the chromophores can be varied in a systematic way. Dendrimers with a controlled number of chromophores at the rim fulfill those requirements perfectly. A detailed photophysical study of a second-generation dendrimer, containing eight peryleneimide chromophores at the rim, was performed 'J. Am. Chem. Soc., 122 (2000) 9278'. One of the most intriguing findings was the presence of collective on/off jumps in the fluorescence intensity traces of the dendrimers. This phenomenon can be explained by assuming a simultaneous presence of both a radiative trap (energetically lowest chromophoric site) and a non-radiative trap (triplet state of one chromophore) within one individual dendrimer. It was shown that an analogue scheme could explain the collective on/off jumps in the fluorescence intensity traces of the photosynthetic pigment B-phycoerythrin (B-PE) (Porphyridium cruentum). The different values of the triplet lifetime that could be recovered for a fluorescence intensity trace of B-PE were correlated with different intensity levels in the trace, suggesting different chromophores acting as a trap as function of time.

Bile Pigments↗
PubMed2001

A new analysis method of single molecule fluorescence using series of photon arrival times: theory and experiment.

Up to now, single molecule fluorescence experiments were performed by dividing the time into a set of intervals and to observe the number of fluorescence photons arriving in each interval. It is obvious that the detected photons carry less information than the arrival times of the photons themselves. From the arrival times, one can still calculate the number of photons in any user-defined interval; whereas, when only the number of photons in an interval are recorded, information about their positions in time is lost. Therefore, we present a new analysis method of single molecule fluorescence data based on the positions in time of the detected fluorescence photons. We derive mathematically different statistical characteristics describing the single molecule fluorescence experiment assuming an immobilized molecule. The theory of point processes using the generating functionals formalism is ideally suited for a consistent description, linking the statistical characteristics of the excitation and detected photons to the statistical characteristics of the single motionless molecule. We then use computer-generated data sets mimicking the single molecule fluorescence experiment to explore the parametric estimation of mono- and bi-exponential single molecule impulse response functions (SMIRFs) via the following statistical characteristics: the probability density distributions (pdd) of the single and first photocount time positions in a user-defined detection interval, the probability distribution of the number of photocounts per user-defined detection interval, the time correlation function and the pdd of the time interval between two consecutive photocounts. It is shown that all of the above characteristics ensure a satisfactory recovery of the decay time of mono-exponential SMIRFs for a broad range of excitation intensities and widths of user-defined detection intervals. For bi-exponential SMIRFs, the selection of the experimental conditions is more critical and dependent on the detection procedure. At lower excitation intensities it is advantageous to use the pdds of the single and first photocount time occurrences in the user-defined detection interval. To show the practical usefulness of the new analysis method, series of photon arrival times from immobilized single molecules of DiI and rhodamine 6G were analyzed to estimate triplet lifetimes and intersystem crossing yields.

Biophysical Phenomena↗
PubMed2001

Intramolecular energy hopping and energy trapping in polyphenylene dendrimers with multiple peryleneimide donor chromophores and a terryleneimide acceptor trap chromophore.

Intramolecular Förster-type excitation energy transfer (FRET) processes in a series of first-generation polyphenylene dendrimers substituted with spatially well-separated peryleneimide chromophores and a terryleneimide energy-trapping chromophore at the rim were investigated by steady-state and time-resolved fluorescence spectroscopy. Energy-hopping processes among the peryleneimide chromophores are revealed by anisotropy decay times of 50--80 ps consistent with a FRET rate constant of k(hopp) = 4.6 ns(-1). If a terryleneimide chromophore is present at the rim of the dendrimer together with three peryleneimide chromophores, more than 95% of the energy harvested by the peryleneimide chromophores is transferred and trapped in the terryleneimide. The two decay times (tau(1) = 52 ps and tau(2) = 175 ps) found for the peryleneimide emission band are recovered as rise times at the terryleneimide emission band proving that the energy trapping of peryleneimide excitation energy by the terryleneimide acceptor occurs via two different, efficient pathways. Molecular- modeling-based structures tentatively indicate that the rotation of the terryleneimide acceptor group can lead to a much smaller distance to a single donor chromophore, which could explain the occurrence of two energy-trapping rate constants. All energy-transfer processes are quantitatively describable with Förster energy transfer theory, and the influence of the dipole orientation factor in the Förster equation is discussed.

Journal Article↗
PubMed2001

An experimental comparison of the maximum likelihood estimation and nonlinear least-squares fluorescence lifetime analysis of single molecules.

Two procedures based on the weighted least-squares (LS) and the maximum likelihood estimation (MLE) method to confidently analyze single-molecule (SM) fluorescence decays with a total number (N) of 2,500-60,000 counts have been elucidated and experimentally compared by analyzing measured bulk and SM decays. The key observation of this comparison is that the LS systematically underestimates the fluorescence lifetimes by approximately 5%, for the range of 1,000-20,000 events, whereas the MLE method gives stable results over the whole intensity range, even at counts N less than 1,000, where the LS analysis delivers unreasonable values. This difference can be attributed to the different statistics approaches and results from improper weighting of the LS method. As expected from theory, the results of both methods become equivalent above a certain threshold of N detected photons per decay, which is here experimentally determined to be approximately 20,000. In contrast to the bulk lifetime distributions, the SM fluorescence lifetime distributions exhibit standard deviations that are sizably larger than the statistically expected values. This comparison proves the strong influence of the inhomogenuous microenvironment on the photophysical behavior of single molecules embedded in a 10-30-nm thin polymer layer.

Journal Article↗
PubMed2001

Primary intraepithelial sebaceous gland carcinoma of the palpebral conjunctiva.

Sebaceous gland carcinoma usually arises from meibomian or Zeis glands deep within the eyelid, but it can rarely arise within the conjunctival epithelium without a deep component. We describe a woman with a history of chronic blepharoconjunctivitis unresponsive to topical medications. Examination disclosed confluent papillary hypertrophy of the upper palpebral conjunctiva and deposits of white flaky material. Tarsoconjunctival punch biopsy revealed intraepithelial sebaceous gland carcinoma. Management consisted of frozen section-controlled complete tumor excision with removal of the entire posterior lamella of the right upper eyelid, cryotherapy to the margins, and reconstruction. Histopathologic analysis confirmed primary sebaceous gland carcinoma localized to the conjunctival epithelium without involvement of underlying meibomian or Zeis glands or the caruncle. Patients with unexplained chronic unilateral blepharoconjunctivitis or papillary hypertrophy of the palpebral conjunctiva should be considered for biopsy to rule out neoplasia, even when there is no sign of an underlying eyelid mass.

Adult↗
PubMed2001

Angle-closure glaucoma in association with orbital pseudotumor.

PURPOSE: To describe the pathophysiology of angle-closure glaucoma secondary to idiopathic inflammatory orbital pseudotumor. DESIGN: Retrospective, small noncomparative case series. PARTICIPANTS: Three patients with angle-closure glaucoma and orbital pseudotumor. METHODS: The pathophysiology of this entity was investigated using magnetic resonant imaging (MRI) and ultrasound biomicroscopy (UBM). MAIN OUTCOMES MEASURES: Clinical features, anterior chamber angle configuration, and intraocular pressure. RESULTS: Angle closure from anterior rotation of the ciliary body caused by choroidal effusions secondary to pseudotumor was demonstrated using MRI and UBM. Two of the three cases resolved after treatment for orbital pseudotumor. CONCLUSIONS: Idiopathic orbital pseudotumor is a cause of secondary angle-closure glaucoma. The mechanism of angle closure is anterior rotation of the ciliary body secondary to choroidal effusions resulting from the orbital inflammation.

Adult↗
PubMed2001

Tarsorrhaphy: clinical experience from a cornea practice.

PURPOSE: To evaluate indications, success rate, and complications of tarsorrhaphy in a cohort of cornea and external disease patients. METHODS: In this study, charts of patients who underwent tarsorrhaphies from January 1, 1995, to September 30, 2000, were retrospectively evaluated. Information reviewed included patient age and sex, indication for tarsorrhaphy, duration of signs and symptoms before tarsorrhaphy, time to epithelial healing after tarsorrhaphy, type of tarsorrhaphy (temporary/permanent), complications, timing of tarsorrhaphy removal, recurrence of signs and symptoms after complete or partial opening of the tarsorrhaphy, number of tarsorrhaphies needed to be replaced or extended, and duration of follow up. RESULTS: Seventy-seven patients were included in this study. Indications for a tarsorrhaphy were persistent epithelial defects or other ocular surface problems associated with neurotrophic ulcers, penetrating keratoplasty (PK), postinfection, exposure keratopathy, surgery other than PK, dry eye syndrome, radiation keratopathy, ocular cicatricial pemphigoid, Stevens-Johnson syndrome, entropion, and application of tissue adhesive. The epithelial defects in 70 (90.9%) of the 77 eyes completely resolved. Overall, the mean duration of signs and symptoms before tarsorrhaphy was 89.8 +/- 27.8 days, and time-to-healing after tarsorrhaphy was 18.0 +/- 2.0 days. The difference between the duration of the signs and symptoms before tarsorrhaphy and time-to-healing after tarsorrhaphy was statistically significant ( p = 0.01). Of the 77 tarsorrhaphies, 24 (31.2%) were temporary and 53 (68.8%) were permanent. Complications after tarsorrhaphy included trichiasis, adhesion between upper and lower lids after tarsorrhaphy lysis, premature opening of the temporary tarsorrhaphy, pyogenic granuloma, and keloid formation of the eyelid. CONCLUSION: Tarsorrhaphy is a very effective and safe procedure in the management of nonhealing epithelial defects and other surface problems, with a 90.9% success rate and only minor complications.

Adolescent↗
PubMed2001

Image-guided transorbital roof craniotomy via a suprabrow approach: a surgical series of 72 patients.

OBJECTIVE: Many subfrontal and orbitofrontal craniotomy techniques have been developed. We present our results with the transorbital roof craniotomy, a frontal craniotomy that incorporates the orbital roof and is performed via a suprabrow incision. This technique was used in 72 patients, primarily for tumor resection. METHODS: Charts were retrospectively reviewed for all patients undergoing transorbital procedures. A total of 72 patients underwent 82 transorbital craniotomies from September 1995 to July 1999. The primary indication for the transorbital approach was mass lesion of the orbit, anterior fossa, or parasellar region. RESULTS: A total of 47 women and 25 men with a mean age of 53 years underwent 82 procedures. The primary pathological finding was meningioma, which occurred in 40 patients (55.6%), followed by craniopharyngioma (6.9%), pituitary macroadenoma (6.9%), schwannoma (5.5%), and hemangioma (5.5%). Simpson Grade I or II resection was achieved in 54% of patients, with Simpson Grade III to V resection achieved in the remaining 46%. Forty-one patients presented with visual loss in 43 cases, with 44.2% experiencing postoperative visual improvement, 46.5% remaining unchanged, and 9.3% worsening. Overall morbidity was 18.4%, with cerebrospinal fluid leak being the most common complication (6.6%). No patients died. CONCLUSION: The transorbital roof craniotomy is an evolutionary approach that provides excellent exposure to the orbit, anterior fossa, and parasellar region with little significant morbidity and, in our series, no mortality. Although we have used this approach primarily for resection of mass lesions, future directions for this procedure will likely lie in treating vascular lesions and lesions of the interpeduncular fossa.

Adult↗
PubMed2001

Update on orbital trauma.

Several advances in orbital trauma are presented. From new techniques in radiologic imaging, the use of endoscopy, and new treatment indications for certain types of fractures. Many of these advances result in decreased morbidity and improved functional results in the treatment of orbital and periorbital trauma.

Eye Injuries↗
PubMed1999

Ophthalmic plastic applications of acellular dermal allografts.

PURPOSE: Clinical problems of contracted conjunctival fornices, superior sulcus defects, and soft tissue contour defects in the periorbital region have not shown good, sustained results with a range of autologous and alloplastic implants. AlloDerm (Lifecell Corp., Woodlands, TX) is an acellular dermal graft processed from human donor tissue. The authors sought to assess the efficacy of AlloDerm as a soft tissue replacement in a variety of oculoplastic applications. DESIGN: Retrospective, noncomparative case series. PARTICIPANTS: Twenty-three patients. METHODS: Applications were broadly classified as barrier/scaffolding (i.e., primary and secondary implant coverage, lid spacer graft) and volume augmentation (i.e., superior sulcus and other periorbital soft tissue contour defects). Barrier grafts were applied as single sheets. Stacked sheets or rolled grafts were used for augmentation. Collectively, this material was used in 29 cases with 3 to 16 months' follow-up. MAIN OUTCOME MEASURES: Clinical evaluation of outcome and complications. RESULTS: As a soft tissue scaffolding and barrier implant, AlloDerm persisted sufficiently to permit repopulation with native tissue. Rolled/stacked implants demonstrated unpredictable resorption. Upper eyelid grafts seemed to have higher resorption rates than lower eyelid grafts. One case of anophthalmic superior sulcus augmentation required two revision surgeries to provide sufficient volume augmentation. The grafts were well tolerated, with no cases of infection or explanation. CONCLUSION: Acellular human dermis is an excellent barrier and reconstructive grafting material that provides an alternative to autologous grafts and other alloplastic material, avoids harvesting autologous tissue, possesses excellent handling properties, and is associated with minimal inflammation. Long-term follow-up is required to evaluate persistence.

Coated Materials, Biocompatible↗
PubMed1999

Pyruvate and lactate protect striatal neurons against N-methyl-D-aspartate-induced neurotoxicity.

A sustained release of glutamate contributes to neuronal loss during cerebral ischaemia. Using cultured mouse striatal neurons, we observed that glucose deprivation, which occurs in this pathological process, enhanced the N-Methyl-D-aspartate (NMDA)- or alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA)-induced neurotoxicity. The end products of glycolysis, lactate and pyruvate, strongly protected neurons from these neurotoxic effects. The neuroprotective effect of pyruvate (which is more prominent in the absence of glucose) was not related to its ability to react with H2O2 by a decarboxylation process. Pyruvate and L-lactate strongly counteracted the deep decrease in the neuronal ATP content induced by NMDA, indicating that they might protect striatal neurons by rescuing cellular energy charge. Addition of MK-801 after the NMDA withdrawal completely protected neurons, suggesting that NMDA neurotoxicity resulted from a delayed NMDA receptor activation probably linked to a delayed release of an endogenous agonist in the extracellular medium. The strong accumulation of extracellular glutamate which was found in both sham and NMDA-treated cultures was markedly decreased by pyruvate. Thus, pyruvate might also exert its protecting activity by decreasing the delayed accumulation of glutamate which seemed to be neurotoxic only after a preexposure of neurons to NMDA.

Adenosine Triphosphate↗
PubMed1999

Advances in the management of lower eyelid retraction.

The purpose of this article is to describe the newer surgical techniques and materials available for repair of lower eyelid retraction. The anatomic basis, classification, and prevention of lower eyelid retraction are explored, as well as traditional methods of surgical management. Two case reports involving the successful use of acellular human dermis (AHD) for lower eyelid retraction are presented. Lower eyelid retraction is associated with a variety of etiologies, which mandate that the surgical repair be directed toward correction of the anatomic abnormality in each patient. Each surgical procedure and material used in the repair of eyelid retraction is associated with unique advantages and disadvantages. AHD has found multiple uses in oculoplastics, including reconstruction of the middle and posterior lamellae in eyelid retraction. An understanding of the mechanistic basis of lower eyelid retraction and familiarity with newer techniques and materials enable the oculoplastic surgeon to modify and individualize the operative repair, resulting in better surgical outcomes.

Blepharoplasty↗
PubMed1999

Removal of orbital apex hemangioma using new transorbital craniotomy through suprabrow approach.

PURPOSE: To describe a technique combining the expertise of the oculoplastic orbital surgeon and the neurosurgeon which allows access to the posterior orbit, anterior fossa, cavernous sinus and suprasellar region with minimal brain manipulation. METHODS: A transorbital craniotomy through a suprabrow incision is performed removing part of the frontal bone and orbital roof as a single piece. This allows wide access with only minimal, if any, brain retraction. The superior, lateral and medial orbit is clearly visualized, as well as the apex of the orbit. The bone flap is replaced at the end of the case with Tantalum plates. RESULTS: A cavernous hemangioma at the orbital apex was removed without complications. The exposure was superb and allowed identification and preservation of orbital structures. CONCLUSIONS: Transorbital craniotomy allows for wide access to the posterior orbit and parasellar region and anterior fossa of the brain with minimal brain manipulation. The use of a suprabrow incision results in an excellent cosmetic result. There is minimal postoperative morbidity, which decreases hospitalization time.

Adult↗
PubMed1998

Balloon catheter dilation for treatment of adults with partial nasolacrimal duct obstruction: a preliminary report.

PURPOSE: The purpose of this study is to determine the efficacy and morbidity of balloon catheter dilation for treatment of partial acquired nasolacrimal duct obstruction in adults with epiphora. METHODS: We performed balloon dacryocystoplasty prospectively on a series of 15 partial nasolacrimal duct obstructions in 13 adults with epiphora. Partial obstruction was diagnosed by a negative Jones-1 test and canalicular irrigation revealing simultaneous reflux through the opposing punctum and drainage into the nose. Balloon dacryocystoplasty was performed under local anesthesia using an antegrade insertion technique. Silicone intubation of the nasolacrimal system was performed immediately after balloon catheter dilation, and the tubes were removed 2 months postoperatively. RESULTS: Success was measured objectively and subjectively at follow-up examinations 2 months and 6 months after the procedure. At 2 months, 11 (73%) of 15 obstructions were open on irrigation, with subjective success (Munk, grade 0 or grade 1) reported in 13 (87%) of 15 obstructions. At 6 months, 11 (73%) of 15 obstructions were open on irrigation, with subjective success (Munk, grade 0 or grade 1) reported in 9 (60%) of 15 obstructions. CONCLUSIONS: Balloon dacryocystoplasty may be a satisfactory primary treatment for adults with acquired partial nasolacrimal duct obstruction who exhibit no clinical signs of chronic infection. Additional long-term observations following balloon dacryocystoplasty are required.

Adult↗
PubMed1998

Enhancement of the cosmetic and functional outcome of enucleation with the conical orbital implant.

OBJECTIVE: The authors evaluated a new design of a conical-shaped enucleation implant to help minimize the occurrence of superior sulcus defects and maximize motility of the prosthesis. The implant shape is a modification of a sphere. It has a posterior conical projection paralleling the orbital walls, a superior projection supporting the soft tissues of the upper eyelid sulcus, a flattened anterior surface, and channels for each rectus muscle. DESIGN: The study design was a consecutive case series from the Oculoplastics and Orbital Service of the Massachusetts Eye and Ear Infirmary. INTERVENTION/PARTICIPANTS: A total of 45 patients (average age, 40 years; range, 13-75 years) had placement of a conical implant (39 primary enucleations, 6 secondary implants) with a minimum of 1 year' follow-up (range, 12-36 months). All of the primary enucleations and two of the secondary procedures had the anterior portion of the implant covered with autologous fascia. Four of the secondary implants were covered with pseudocapsule harvested from the explanted primary implant. Prostheses were fit 6 to 10 weeks after surgery. MAIN OUTCOME MEASURES: Postoperative appearance of patients was assessed by qualitative appearance of the superior sulcus and prosthetic motility, and subjectively by patients' satisfaction. RESULTS: A total of 43 patients had minimal or no superior sulcus defect, whereas 2 patients had moderate defects. There were no severe sulcus defects. All patients were satisfied with their appearance and did not seek further surgery to correct any upper sulcus asymmetry. Prosthetic motility with small-angle ductions (<10 degrees) and saccades was good in all cases. There were two cases of conjunctival wound dehiscence. Both occurred within 4 weeks of surgery. One wound dehiscence was sutured, whereas the other healed spontaneously. There were no cases of implant extrusion, migration, or infection. CONCLUSION: The conical orbital implant provides appropriate reconstitution of orbital volume while minimizing superior sulcus defects with adequate prosthetic motility.

Adolescent↗