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Biomedical subjects

J H Baker

Publications and source records attributed to J H Baker.

At least 19 recordsLinked to original sources
PubMed1992

Paraplegia and traumatic rupture of the aorta: a disease process or surgical complication?

Surgical repair of traumatic rupture of the aorta results in an excellent survival rate especially among the young, although paraplegia continues to be a serious postoperative complication. The authors present nine cases admitted to Stoke Mandeville Hospital, England, including detailed post-mortem findings on one of the cases. Although it was difficult to be certain of the patients' general and neurological status prior to surgery, as it was not well documented in the patients' case notes, it was evident that systemic hypotension and poor distal aortic perfusion were responsible for the disabling complication. A review of the initial medical management of these patients and the surgical techniques employed in repairing such injuries is urgently needed.

Accidents, Traffic↗
PubMed1991

Muscle regeneration following segmental necrosis in tenotomized muscle fibers.

The aim of this study was to determine how the new myotendinous junctions were re-established at the proximal and distal ends of the soleus muscle after tenotomy. Both proximal and distal tendons of the soleus muscle in mature female rats were severed. The animals were killed and the soleus muscles were removed and prepared for light and electron microscopic examination 1, 3, 5, 7, 14, 21, 28, and 42 days after the operation. It was found that segmental fiber destruction followed by removal by macrophages occurred at the ends of the soleus muscle fibers. This resulted in the liberation and myogenic activation of satellite cells. By 3 days after tenotomy the fusion of myoblasts to form myotubes could be seen. The myotubes developed within the original basal lamina and reattached to the surviving non-necrotic segments and grew in both length and width so that by 6 weeks postoperation, normal myotendinous junctions had been reformed. This study is the first to show that re-establishment of the myotendinous junction following tenotomy is accomplished by regeneration of the necrotic ends of the tenotomized fibers.

Animals↗
PubMed1990

Association of iron-containing astrocytes with dopaminergic neurons of the arcuate nucleus.

Specialized astrocytes, identified by cytoplasmic granules that are electron-dense and vividly stained by toluidine blue due to the presence in the granules of SH molecules and molecules of iron, have long been known to be present within the arcuate nucleus of the hypothalamus. Their function, however, is obscure. To determine whether or not these specialized astrocytes are in contact with dopaminergic neurons, rat brain sections were stained to detect tyrosine hydroxylase (TH) immunoreactive neurons by immunocytochemistry and were examined by both light and electron microscopy. Iron-rich astrocytes were located in the same general portion of the arcuate nucleus as were TH+ neurons, and most appeared closely associated with TH+ structures (somas, dendrites, and fibers) at the light-microscopic level. At the ultrastructural level, close contact between TH + neurons and processes of iron-rich glia was confirmed. This unique anatomical association suggests a functional relationship between the two cell types that may be related to unusual histochemical features of both cell types and/or to the location of these cells in an area with a highly permeable blood-brain barrier.

Animals↗
PubMed1989

Fungemia caused by an amphotericin B-resistant isolate of Sporothrix schenckii. Successful treatment with itraconazole.

A 58-year-old, alcoholic, diabetic man presented with multiple, ulcerated skin lesions and polymicrobial septicemia. Sporothrix schenckii was recovered from blood cultures and was resistant to amphotericin B by in vitro testing. Amphotericin B therapy failed, but the patient responded dramatically to itraconazole therapy, only to relapse 3 months after therapy was stopped. Reinstitution of itraconazole therapy has produced another dramatic response. This report is noteworthy for three reasons. First, to our knowledge, it represents only the second reported instance of fungemia with S schenckii that responded to medical therapy. Second, it illustrates that in vitro antifungal susceptibility tests may predict clinical infection response to drug therapy. Third, it suggests that itraconazole has significant promise in treating systemic sporotrichosis.

Amphotericin B↗
PubMed1988

Adaptation of skeletal muscle to immobilization in a shortened position.

This study determined the morphological changes and adaptations that occur following immobilization of rat soleus and gastrocnemius muscles when the ankle joint is placed in complete plantar flexion for 2, 5, 7, 14, 21, and 28 days by means of plaster casts. Previous studies of such shortened muscles have shown that the number of sarcomeres in series is reduced, but how the sarcomeres are reduced has not been determined. We observed that the fibers in the mid-belly region of the muscles demonstrated a progressive degenerative process over the first few weeks. Myofibrils across the entire width of the affected fibers underwent dissolution. However, by 4 weeks new myofibrils were being formed, and sarcomere lengths appeared normal. Portions of the fibers near the tendon underwent segmental necrosis. These findings are similar to the response of the soleus and gastrocnemius muscles to tenotomy and are clinically relevant to orthopedic procedures that maintain muscles in shortened conditions for prolonged periods.

Adaptation, Physiological↗
PubMed1988

Eosinophilia, respiratory symptoms and pulmonary infiltrates in rubber workers.

This report describes a spectrum of respiratory illnesses associated with eosinophilia which occurred in a group of workers exposed to fumes from a synthetic rubber-based curing operation. Respiratory syndromes induced by this exposure included an acute sensitizing illness with dyspnea and wheezing in some workers and pulmonary infiltrates with eosinophilia in others. Another worker developed chronic obstruction of the airways with recurrent bronchitic illnesses. Mild to marked peripheral eosinophilia, up to 3,000/cu mm, was usually present in the symptomatic workers and in 11 of 30 asymptomatic workers. These cases illustrate the diversity of respiratory illnesses which may result from a common workplace exposure and reinforce the importance of considering occupational exposures in the differential diagnosis of peripheral eosinophilia.

Acute Disease↗
PubMed1987

Calcium-activated protease activity in tenotomized muscle.

The purpose of this study was to investigate the possible role of calcium-activated neutral protease in the disorganization and dissolution of the myofibrils of the rat soleus that occurs following tenotomy. Rats were killed 3, 5, 7, 14, 21, and 42 days after tenotomy of the soleus, and the muscles were removed and assayed for calcium-activated protease activity. Maximal protease activity occurred 1 week after tenotomy, at the time when myofibril organization is completely disrupted. Activity was still high 2 and 3 weeks after the operation, but returned to normal levels by 6 weeks, when muscle histology had returned to normal. The time course of the calcium-activated protease activity corresponded closely to the time course of the morphological changes. Thus, calcium-activated neutral protease may play a major role in myofibrillar proteolysis following tenotomy and in making the myofibril susceptible to proteolytic attack by other, less specific proteases.

Animals↗
PubMed1987

Degeneration and alteration of axons and intrafusal muscle fibers in spindles following tenotomy.

The effect of tenotomy (cutting of distal and proximal tendons) on the spindles in soleus muscle of adult rats was examined by light and electron microscopy in tissue obtained 1, 2, 3, 4, 5, 6, 7, and 14 days after surgery. Degenerative changes in the spindles progressed with time; also, the degree of alteration observed in a spindle varied with its position in the muscle, i.e., the earliest and most extensive changes occurred in spindles situated near the tendons. The disorganization and breakdown of myofibrils in the intrafusal muscle fibers were observed 3 days after tenotomy and continued with longer periods after surgery. The progression of morphological changes included alteration in fiber outline and the external lamina of the intrafusal muscle fibers and changes in the extracellular environment within the spindle capsule. The intrafusal muscle fibers of some spindles were shortened, apparently due to the loss of their polar ends, and degenerated axons which apparently supplied the intrafusal muscle fibers were also observed. Completely necrotic intrafusal fibers were absent. A possible relationship between the observed morphologic alterations and an adjustment of the spindle to muscle shortening is discussed.

Animals↗
PubMed1987

Hysterical paraplegia.

Between 1944 and 1984 20 patients were admitted to a spinal injuries centre with a diagnosis of traumatic paraplegia. They subsequently walked out and the diagnosis was revised to hysterical paraplegia. A further 23 patients with incomplete traumatic injuries, who also walked from the centre, have been compared with them as controls. The features that enabled a diagnosis of hysterical paraplegia to be arrived at were: They were predominantly paraplegic, There was a high incidence of previous psychiatric illness and employment in the Health Service or allied professions, Many were actively seeking compensation. The physical findings were a disproportionate motor paralysis, non anatomical sensory loss, the presence of downgoing plantar responses, normal tone and reflexes. They made a rapid total recovery. In contrast, the control traumatic cases showed an incomplete recovery and a persistent residual neurological deficit. Investigations apart from plain radiographs of the spinal column were not warranted, and the diagnosis should be possible on clinical grounds alone.

Female↗
PubMed1986

Peripheral eosinophilia and respiratory symptoms in rubber injection press operators: a case-control study.

To evaluate a suspected association between an outbreak of acute respiratory illness and eosinophilia and employment as a rubber worker, we performed a retrospective review of medical records of rubber workers employed from September 1983 to July 1984 in a plant housing a thermoinjection process. Twenty-five workers met the case definition of a respiratory illness requiring a physician visit. The predominant respiratory illness was acute in onset with cough, chest tightness, and dyspnea. Peripheral eosinophilia, up to 40% of white blood cells in a peripheral smear, was seen in 10 of 18 (56%) cases. Twenty-one of 25 white males with respiratory symptoms were employed in the thermoinjection process (odds ratio = 22, p less than .001). Smoking and employment in this process contributed independently to an increased risk of being a case as determined by a logistic regression analysis. Return to the plant building caused recurrence of symptoms in most cases, and these workers have been transferred or left the company. We conclude that a strong previously unrecognized association exists between employment in this neoprene rubber thermoinjection process and the development of an acute respiratory illness.

Adult↗
PubMed1985

The development of central cores in both fiber types in tenotomized muscle.

Using the histochemical reaction for myosin adenosine triphosphatase (ATPase), a study of the rat soleus muscle following tenotomy was undertaken. It was demonstrated that both type 2A and 2C fibers undergo degenerative changes following tenotomy. All previous studies have stated that only type 1 fibers were affected and developed central core lesions and that type 2 fibers were somehow protected from the degenerative process. The results of this experiment illustrate that central core lesions will develop in all three fiber types (types 1, 2A, and 2C) of the soleus following tenotomy.

Adenosine Triphosphatases↗
PubMed1984

Traumatic cerebral flaccid paraplegia.

Two cases of paraplegia caused by head injuries sustained in recent military conflicts are presented. The underlying pathological disturbances could be related to the CT scan appearances and are discussed in the light of previously reported series. Both cases were remarkable for an early and prolonged paraplegia which was flaccid, rather than spastic, and for the sensory impairment produced.

Adult↗
PubMed1984

Atropine toxicity in acute cervical spinal injury.

A patient with a C.3/C.4 fracture dislocation resulting in an incomplete tetraplegia was treated with Cimetidine 400 mg bd to prevent gastrointestinal bleeding and 0.6 mg of atropine 6 hourly. He developed symptoms of atropine poisoning in the form of hallucinations, confusion and dilated pupils when the total dosage of atropine was 2.8 mg. This is far below the toxic levels normally considered necessary to produce atropine poisoning. The patient recovered. In view of the fact that this combination of drugs may be used in spinal units to prevent gastrointestinal bleeding and bradycardia, this experience is reported.

Adult↗
PubMed1983

Ultrastructural and biochemical changes in rat soleus muscle following tenotomy.

This study was designed to correlate changes in the rate-limiting enzymes of glycogen synthesis (glycogen synthase) and glycogen breakdown (glycogen phosphorylase) with the ultrastructural changes which occur in the soleus muscle following tenotomy. Soleus muscles were removed at 1, 2, 3, 7, 14, 21, and 63 days after tenotomy and were prepared for electron microscopy or frozen for enzyme analysis. In the first 7 days posttenotomy, soleus muscle fibers underwent a series of degenerative changes, while both synthase and phosphorylase activities decreased. Over the next 8 weeks the histological appearance of the soleus muscle eventually returned to normal while synthase and phosphorylase activities increased. We suggest that recovery from tenotomy involves an increase in the energy demands of the muscle, resulting in the increased activity of the key rate-limiting enzymes of muscle glycogen metabolism from the drastically reduced levels observed in the period before recovery begins.

Animals↗