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Biomedical subjects

A M MacLeod

Publications and source records attributed to A M MacLeod.

At least 163 records · Page 9Linked to original sources
PubMed1978

Digital replantation: clinical experiences.

In a series of 130 digital replantations successful revascularization has been obtained in 74% of cases. Arterial thrombosis is the most common cause (65%) of all failures. A useful digit can be obtained following replantation and the surgery is particularly indicated for amputated thumbs and in hands suffering multiple injuries. Precautionary measures against bleeding are absolutely essential. Primary tendon and nerve repairs are advocated. Vascular occlusion may be corrected by revisional surgery and secondary surgery can improve tendon nerve or joint function.

Adolescent↗
PubMed1977

Microsurgery.

Explore the source record for details and available documents.

Adolescent↗
PubMed1977

A long-term review of digital replantation.

An analysis of the first 130 cases of digital revascularization and replantation performed at St Vincent's Hospital, Melbourne, during the period 1970-1977, confirms the long-term functional value of these procedures provided that strict indications for replantation are adhered to. Patient satisfaction has been almost universal, and objective testing shows that the most satisfying aspect of the procedure is the quality of sensory return. Flexor tendon function and the range of joint movement, however, are universally poor, and all patients complain of sensitivity to cold. The thumb has been by far the most satisfactory digit to replant, and avulsion injuries gave the poorest results, from the point of view of both survival and long-term function.

Adolescent↗
PubMed1977

Evaluation of digital replantation--a review of 100 cases.

One hundred digital replantations and revascularizations of digits performed during a five year period were analyzed. Seventy replantations (70 per cent) survived and 62 were available for long term functional follow-up. Provided strict indications are observed, replantation is a most worthwhile procedure.

Adolescent↗
PubMedDate not supplied

Practice-related changes in human brain functional anatomy during nonmotor learning.

Practice of a novel task leads to improved performance. The brain mechanisms associated with practice-induced improvement in performance are largely unknown. To address this question we have examined the functional anatomy of the human brain with positron emission tomography (PET) during the naive and practiced performance of a simple verbal response selection task (saying an appropriate verb for a visually presented noun). As a control state, subjects were asked to repeat the visually presented nouns. Areas of the brain most active during naive performance (anterior cingulate, left prefrontal and left posterior temporal cortices, and the right cerebellar hemisphere), compared to repeating the visually presented nouns, were all significantly less active during practiced performance. These changes were accompanied by changes in the opposite direction in sylvian-insular cortex bilaterally and left medial extrastriate cortex. In effect, brief practice made the cortical circuitry used for verbal response selection indistinguishable from simple word repetition. Introduction of a novel list of words reversed the learning-related effects. These results indicate that two distinct circuits can be used for verbal response selection and normal subjects can change the brain circuits used during task performance following less than 15 min of practice. One critical factor in determining the circuitry used appears to be the degree to which a task is learned or automatic.

Adult↗
PubMedDate not supplied

Multiple foci in parietal and frontal cortex activated by rubbing embossed grating patterns across fingerpads: a positron emission tomography study in humans.

Somatosensory representations occupy parietal postcentral gyral (S1) and lateral sulcal-opercular cortex (S2). To address the issue of possible multiple activation foci in these regions and possible differences due to stimulating skin directly or through an imposed tool, we studied changes in cerebral blood flow with positron emission tomography during passive tactile stimulation of one or two fingertips. Restrained fingers were rubbed with embossed gratings using a rotating drum stimulator in 11 subjects. For different scans, gratings touched the skin directly for optimal stimulation of cutaneous receptors (called skin mode stimulation) or indirectly through an imposed guitar plectrum snugly fitted to the same fingers (called tool mode stimulation). The latter was expected to stimulate deep receptors better. Subjects estimated roughness after each scan. Direct skin contact activated statistically validated foci in both hemispheres. On the contralateral side these foci occurred in the anterior and posterior limbs of the postcentral gyrus and on the ipsilateral side only in the posterior limb. Tool mode stimulation activated one contralateral focus that was in the posterior limb of the postcentral gyrus. These results suggest at least two maps for distal fingertips in S1 with the anterior and posterior foci corresponding, respectively, to activations in area 3b and the junction between areas 1 and 2. In contralateral S2, skin mode stimulation activated a peak that was anterior and medial to a focus associated with tool mode stimulation. The magnitude of PET counts contralateral to stimulation was greater in the anterior S1 and the S2 regions during initial scans but reversed to more activation in the posterior S1 during later scans. These short-term practice effects suggest changes in neural activity with stimulus novelty.

Adult↗
PubMedDate not supplied

Tactile attention tasks enhance activation in somatosensory regions of parietal cortex: a positron emission tomography study.

We used positron emission tomography to study cortical regions mediating tactile attention. Cues selectively directed subjects to attend to the roughness or duration of contact with embossed gratings that rubbed against a single fingertip with controlled speed and force. The task required discriminating between paired gratings that differed in tactile features of roughness and/or length. For different blocks of trials, cues directed attention to one tactile feature or indicated a divided attention strategy to a change in either feature. All attention conditions unambiguously activated several somatosensory foci in the parietal cortex, including somatotopically appropriate portions of the primary somatosensory cortex in the postcentral gyrus (S1) and the secondary somatosensory region (S2) within parietal opercular regions. There was no evidence for separate processing foci for selective and divided attention strategies, or for selectively attending to roughness versus stimulus duration. We observed a greater magnitude blood flow change in S2 versus S1 during attention tasks, which suggests that S2 might actually influence S1 activity. Despite these differences, modulation of S1 and S2 supports concepts of early selection in tactile attention. There were also examples of non-sensory foci in frontal cortex, anterior cingulate gyrus and bilateral superior parietal regions at the fundus of the postcentral sulcus. Posterior parietal regions observed in this study did not overlap foci seen in studies of visual attention. Thus, the posterior parietal region may be subdivided into modality-specific subregions, each of which processes information needed to attend to a specific modality. These non-sensory areas may constitute a network that provides a source of modulating influences on the earlier stage, sensory areas.

Adolescent↗
PubMedDate not supplied

Review of a hospital preadmission program: applying the principles of continuous quality improvement.

The importance of hospital preadmission programs is increasing in light of the trend toward shorter lengths of stay. New processes are required to prepare patients for same-day admission, to initiate discharge planning at the earliest possible opportunity and to provide education to patients for which there is now less time during hospitalization. This article presents the process and outcomes of one hospital's review of its preadmission program.

Admitting Department, Hospital↗
PubMedDate not supplied

[FK-506. A new immunosuppressive drug].

In this brief review, we outline the properties of the new macrolide immunosuppressant FK-506. This selective anti-T cell agent has a similar mode of action to cyclospirin A (CSA). It is, however, more powerful, has the capacity (unlike CSA) to reverse liver allograft rejection and appears to have a higher therapeutic index than CSA in patients receiving organ transplants. Preliminary data suggest that renal function is better in recipients of liver transplants given FK-506 as primary therapy compared with those given CSA. In addition, evidence has been presented that FK-506-treated patients have shorter hospital stay than those receiving treatment with CSA. Other factors require to be taken into account, but it may be that it will prove less expensive in the future to treat patients with FK-506 than with CSA. The potential of FK-506 for the control of autoimmune diseases has been demonstrated in rodent models of rheumatoid arthritis, type I diabetes, posterior uveitis, allergic encephalomyelitis and glomerulonephritis. In the clinical field, FK-506 has been used in two cases of nephrotic syndrome resulting from glomerulonephritis; there was improvement in proteinuria and no decline in renal function. Studies to date have been restricted to one clinical centre although many hundreds of organ graft recipients have been studied. Both longer term and multi-centre investigations are urgently required, but it appears that FK-506 may offer considerable potential as an immunotherapeutic agent.

Animals↗