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Biomedical subjects

J M Alexander

Publications and source records attributed to J M Alexander.

At least 91 records · Page 5Linked to original sources
PubMed1980

Sulfhydryl Group Involvement in Plasmalemma Transport of HCO(3) and OH in Chara corallina.

The effect of the sulfhydryl reagents (-SH) p-chloromercuribenzene-sulfonic acid (PCMBS), N-ethylmaleimide (NEM), and inorganic mercury on H(14)CO(3) (-) assimilation in Chara corallina is reported. Commercial grade PCMBS caused severe inhibition of H(14)CO(3) (-) assimilation. Results obtained using purified PCMBS (stock solution passed through a chelating resin) indicated that inhibition observed using unpurified PCMBS was due predominantly to the presence of inorganic mercury (as a contaminant). The inhibitory role of inorganic mercury was verified using HgCl(2). This chemical caused a dramatic inhibition of H(14)CO(3) (-) assimilation, while it had little effect on cellular (14)CO(2) fixation. Reversal of the Hg(2+) inhibition of H(14)CO(3) (-) assimilation (in presence of 1.0 millimolar dithioerythritol) was extremely slow, requiring 2 to 3 hours for the reestablishment of control rates. This slow recovery may reflect de novo synthesis of transport proteins.Almost complete (irreversible) inhibition of H(14)CO(3) (-) assimilation was observed after cells were briefly (2 min) exposed to 0.1 to 0.3 millimolar NEM. At critical concentrations, both inorganic mercury and NEM perturbed the HCO(3) (-) transport system to such an extent that the H(14)CO(3) (-) assimilation versus HCO(3) concentration profiles changed shape. This could reflect a conversion of the transport system to a facilitated diffusion mode. Alternatively, the efficiency of the transport system may have been affected such that HCO(3) (-) efflux increased significantly.The influence of these -SH reagents on the OH(-) efflux system was also investigated. The H(14)CO(3) (-) assimilation and OH(-) efflux results demonstrate the involvement of -SH groups in the plasmalemma transport of both HCO(3) (-) and OH(-) in C. corallina. Greater transport susceptibility to inorganic mercury and NEM compared to purified PCMBS suggested that the sulfhydryl groups were not located on the peripheral surface of the plasmalemma.

Journal Article↗
PubMed1979

Posterior maxillary osteotomies: an aid for a difficult prosthodontic problem.

Patients who have supereruption of posterior dentoalveolar segments provide an interesting challenge to the dentisr. The severe problems require a team approach to achieve the best results. Factors influencing the treatment include the periodontal status of the involved teeth as well as the concern of the patient. The posterior maxillary osteotomy provides the chance to maintain the vital functional teeth in an otherwise difficult situation. It must be emphasized that the patient must wear an opposing splint or prosthesis following surgery to prevent relapse. This conservative approach maintains the teeth and their vitality and anatomically repositions the supererupted segment to an improved functional position.

Adult↗
PubMed1979

An unusual case of trismus.

Described is a case in which a patient suffered multiple facial injuries resulting in significant trismuss. Many extracapsular factors have been reported to results in trismus. Most common are those involving the coronoid process and fibrous tissue adhesions of associated structures. This case involves a situation in which multiple foreign-body fragments led to this patient's being unable to open his mouth adequately.

Adult↗
PubMed1978

Role of pulmonary vascular resistance measurements in preoperative evaluation of candidates for pulmonary resection.

Pulmonary function tests (PFT), arterial blood gases (ABG), lung scanning, and pulmonary artery balloon occlusion with measurement of pulmonary vascular resistance (PVR) have all been used for preoperative evaluation of pulmonary function. These tests, however, do not always accurately predict tolerance to lung resection. We have evaluated a new technique which promises to increase the accuracy of preoperative evaluation of pulmonary function. Utilizing a balloon flotation catheter, we measured PVR at varying cardiac outputs. Forty-five patients underwent this study without morbidity or mortality. Five of 30 patients who subsequently underwent pulmonary surgery died of respiratory failure. All of these deaths were from the high-risk group as determined by PVR. Only one of the five had been judged to be at high risk by PFT and ABG. This technique has the advantages of low morbidity and simplicity and should be especially helpful in the evaluation of those patients who have borderline pulmonary function as determined by the more standard tests.

Aged↗
PubMed1977

Prostaglandin synthesis inhibition restores hypoxic pulmonary vasoconstriction.

Hypoxic pulmonary vasoconstriction in blood-perfused isolated dog lungs progressively diminishes with repeated hypoxic challenges. We investigated the role of prostaglandins in effecting the decay of the hypoxic response by using a double perfusion preparation that could separately perfuse the right and left lungs of a single dog. Degeneration of this response was reversed by the addition of prostaglandin (PG) synthesis inhibitors, aspirin, or indomethacin. Various PG's known to be produced by the lung (PGE1, PGE2, and PGF2alpha), were infused, and only PGE1 abolished hypoxic pulmonary vasoconstriction. Since other workers have shown that lungs can synthesize and release PG's in response to various stimuli, we postulate that PGE1 synthesis in isolated lungs may increase and thereby cause the degeneration of the hypoxic response. The addition of aspirin or indomethacin could inhibit the synthesis of PGE1 and thereby restore hypoxic pulmonary vasoconstriction.

Animals↗
PubMed1976

Effect of angiotensin on hypoxic pulmonary vasoconstriction in isolated dog lung.

The effects of infused angiotensin on hypoxic pulmonary vasoconstriction in blood-perfused isolated dog lungs were studied. By using a double-perfusion system we were able to perfuse the right and left lungs separately in the same animal; one lung was used as control and the other lung was experimentally modified. The vasoconstrictive response to hypoxia decreased with time in the isolated lung preparations. The infusion of either angiotensin I or angiotensin II (1.2-5.8 mug/min) caused a threefold increase in the vasoconstrictive response to hypoxia over control levels. A second hypoxic period during the infusion usually yielded a diminished response, suggesting further degeneration of the response irreversible with angiotensin. It was concluded that angiotensin I or angiotensin II temporarily enhances hypoxic pulmonary vasoconstriction in isolated dog lungs.

Angiotensin II↗
PubMed1976

Radionuclide bone scanning in the diagnosis of lesions of the maxillofacial region.

Radionuclide scanning is a safe, simple, sensitive technique for demonstrating lesions of the skeletal system. It has proved to be valuable in the early detection and differential diagnoses of lesions involving the maxillofacial region. Abnormal uptake of a bone scanning agent relies on a disturbance of the mineral metabolism of bone. These changes in the pathophysiology of bone are detected earlier on radioisotope bone scans than on radiographs. Bone scanning is a superior technique for diagnosis when compared to radiographic examination. A positive scan is not pathognomonic of any specific disease, but with the clinical, laboratory, and radiographic findings, it can differentiate many lesions and contribute invaluable information concerning a particular lesion or condition so that treatment can be more effectively planned.

Adult↗
PubMed1976

Alloplastic augmentation of middle-third facial deformities.

In reconstruction of deformities of the middle third of the face, an advantage in the use of an alloplastic implant rather than tissue transplantation is that only one surgical procedure is needed. A more accurate fit and better esthetic results are obtained with custom-made implants of silicone rubber. Carved implants require less fabrication time and offer adequate results although they are not always shaped as accurately.

Adult↗