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Biomedical subjects

J L Smith

Publications and source records attributed to J L Smith.

At least 289 records · Page 16Linked to original sources
PubMed1990

Speed-related changes in hindlimb intersegmental dynamics during the swing phase of cat locomotion.

To determine speed-related changes in hindlimb motion that might account for the mutability of bifunctional (hip extensor/knee flexor) muscle activity during the E1 phase of swing, we studied hip and knee joint kinematics and kinetics during swing over a ten-fold increase in locomotor speed (0.35 to 3.5 m/s). Three cats were filmed (100 frames/s) while locomoting on a motorized treadmill; kinematics were analyzed for the entire step cycle and kinetics for the swing phase. During swing, angular excursions at the hip and knee joints were similar for walking and trotting, but hip flexion and extension were significantly less after the transition from trot to gallop, while knee-angle range of motion increased during gallop phases E1, E2, and E3. During swing, knee-extension velocity peaked early in E1 and increased linearly with speed, while hip-flexion velocity peaked late in the flexion (F) phase and also increased linearly, but decreased precipitously at the trot-gallop transition and remained constant as speed of galloping increased. Muscle torque directions during E1, flexor at the knee and extensor at the hip, were consistent with the proposed role of bifunctional posterior thigh muscles to decelerate thigh and leg segments for paw contact. At the knee joint, muscle torque during E1 counteracted a large interactive torque due to leg angular acceleration; the magnitudes of both torques were speed related with maximal values at the fastest speed tested (3.5 m/s). At the hip joint, muscle torque during E1 also counteracted a large interactive torque due to leg angular acceleration; the magnitudes of these two torques were speed related during the walk and trot, and like hip flexion velocity, decreased at the trot-gallop transition. Our data on speed-related changes in hindlimb dynamics suggest that the E1 burst amplitude (and perhaps duration) of posterior thigh muscles will be speed related during the walk and trot. After the trot-gallop transition at about 2.5 m/s, the recruitment of these bifunctional muscles may decline due to the changes in hindlimb dynamics. Because activity of these muscles counteracts interactive torques primarily related to leg angular acceleration, we suggest that motion-related feedback decoding this action may be important for regulating recruitment during E1.

Animals↗
PubMed1990

Antimony electrodes. Mucosal potential differences and buffer composition adversely affect pH measurements in the stomach.

Antimony electrodes are clinically useful because of their low cost and simple construction; they have no glass to break. There is only a few hundred ohms resistance between an antimony pH electrode and the reference electrode so that the voltage generated can be recorded with simple low-impedance recorders linked to microcomputers. We used antimony pH electrodes with silver-silver chloride electrodes applied to the skin to measure the gastric pH in vivo and obtained erroneously high values. Using an ion-permeable dialysis chamber to surround electrodes in vivo, we showed that the discrepancy was caused by interference from gastric transmucosal potential difference. To circumvent the interference, we used a combination electrode constructed by embedding a monocrystalline antimony electrode and a silver-silver chloride reference electrode in dental acrylic. Antimony pH electrodes calibrated with commercial pH buffers also gave erroneous readings in HCl solutions of known pH. The erroneous readings were due, in part, to organic complex-forming ligands or organic salts such as potassium phthalate present in commercial buffer solutions. Accurate pH calibration can be obtained with citrate or acetate buffers or by using a normogram to correct for the errors introduced with commercial buffers. The combination antimony pH electrode has a number of potential clinical and research applications and simplifies obtaining accurate and reliable pH data in vivo.

Antimony↗
PubMed1990

Lymphomatoid granulomatosis of eyelid and brow with progression to lymphoma.

Lymphomatoid granulomatosis is an uncommon lymphoreticular disease that primarily involves the lungs, skin, and central nervous system and has a high mortality rate. This is the first report in the American literature of lymphomatoid granulomatosis with involvement of the skin of the eyelid and brow. After a protracted clinical course, the patient died of pulmonary complications.

Eyebrows↗
PubMed1990

Clonality of T cell and phenotypically undefined lymphoid neoplasms: the value of genotypic analyses.

The value of genotypic analysis for routine assessment of leukaemia and lymphoma was shown by the findings in a selected series of 30 cases. T cell receptor (TcR) gene rearrangements were observed in six out of nine cases of CD3+ CD8+ lymphocytoses and provided clear evidence for clonality in this group. The T cell proliferations in two of the remaining cases masked B cell lymphocytic leukaemia and hairy cell leukaemia, while in the third case no cause was found for the polyclonal proliferation. Heterogeneity of phenotype and genotype were observed in peripheral T cell lymphomas: one out of six cases showed TcR gene rearrangement, one case retained its germline configuration, a further case masked B cell lymphoma and the remainder were polyclonal. Genotypic analysis was helpful in the analysis of a tumour of mixed T cell and myeloid phenotype which was shown to be germline for TcR and immunoglobulin genes, consistent with a myeloid origin. Two histiocytic tumours were found to have clonal rearrangement of TcR genes. Nine out of 11 B cell tumours showed immunoglobulin gene rearrangement. It is concluded that genetic analyses are useful in the analysis of T cell, histiocytic, and B cell tumours in which an immunoglobulin phenotype cannot be defined.

Antigens, CD↗
PubMed1990

Adaptive control for backward quadrupedal walking. I. Posture and hindlimb kinematics.

1. To gain new perspectives on the neural control of different forms of quadruped locomotion, we studied adaptations in posture and hindlimb kinematics for backward (BWD) walking in normal cats. Data from four animals were obtained from high-speed (100 fr/s) ciné film of BWD treadmill walking over a range of slow walking speeds (0.3-0.6 m/s) and forward (FWD) treadmill walking at 0.6 m/s. 2. Postural adaptations during BWD walking included flexion of the lumbar spine, compared to a relatively straight spine during FWD walking. The usual paw-contact sequence for FWD walking [right hindlimb (RH), right forelimb (RF), left hindlimb (LH), left forelimb (LF)] was typically reversed for BWD walking (RH, LF, LH, RF). The hindlimbs alternated consistently with a phase difference averaging 0.5 for both forms of walking, but the phasing of the forelimbs was variable during BWD walking. 3. As BWD walking speed increased from 0.3 to 0.6 m/s, average hindlimb cycle period decreased 21%, stance-phase duration decreased 29%, and stride length increased 38%. Compared to FWD walking at 0.6 m/s, stride length was 30% shorter, whereas cycle period and stance-phase duration were 17% shorter for BWD walking. For both directions, stance occupied 64 +/- 4% (mean +/- SD) of the step cycle. 4. During swing for both forms of walking, the hip, knee, and ankle joints had flexion (F) and extension (E1) phases; however, the F-E1 reversals occurred earlier at the hip and later at the knee for BWD than for FWD walking. At the ankle joint, the ranges of motion during the F and E1 phases were similar for both directions. During BWD walking, however, the knee flexed more and extended less, whereas the hip flexed less and extended more. Thus horizontal displacement of the limb resulted primarily from hip extension and knee flexion during BWD swing, but hip flexion and knee extension during FWD swing. 5. At the knee and ankle joints, there were yield (E2) and extension (E3) phases during stance for both forms of walking; however, yields at the knee and ankle joints were reduced during BWD walking. At the hip, angular motion was unidirectional, as the hip flexed during BWD stance but extended during FWD stance. Knee extension was the prime contributor to horizontal displacement of the body during BWD stance, but hip extension was the prime contributor to horizontal displacement during FWD stance. 6. Our kinematic data revealed two discriminators between BWD and FWD walking.(ABSTRACT TRUNCATED AT 400 WORDS)

Adaptation, Physiological↗
PubMed1990

Adaptive control for backward quadrupedal walking. II. Hindlimb muscle synergies.

1. To compare the basic hindlimb synergies for backward (BWD) and forward (FWD) walking, electromyograms (EMG) were recorded from selected flexor and extensor muscles of the hip, knee, and ankle joints from four cats trained to perform both forms of walking at a moderate walking speed (0.6 m/s). For each muscle, EMG measurements included burst duration, burst latencies referenced to the time of paw contact or paw off, and integrated burst amplitudes. To relate patterns of muscle activity to various phases of the step cycle, EMG records were synchronized with kinematic data obtained by digitizing high-speed ciné film. 2. Hindlimb EMG data indicate that BWD walking in the cat was characterized by reciprocal flexor and extensor synergies similar to those for FWD walking, with flexors active during swing and extensors active during stance. Although the underlying synergies were similar, temporal parameters (burst latencies and durations) and amplitude levels for specific muscles were different for BWD and FWD walking. 3. For both directions, iliopsoas (IP) and semitendinosus (ST) were active as the hip and knee joints flexed at the onset of swing. For BWD walking, IP activity decreased early, and ST activity continued as the hip extended and the knee flexed. For FWD walking, in contrast, ST activity ceased early, and IP activity continued as the hip flexed and the knee extended. For both directions, tibialis anterior (TA) was active throughout swing as the ankle flexed and then extended. A second ST burst occurred at the end of swing for FWD walking as hip flexion and knee extension slowed for paw contact. 4. For both directions, knee extensor (vastus lateralis, VL) activity began at paw contact. Ankle extensor (lateral gastrocnemius, LG) activity began during midswing for BWD walking but just before paw contact for FWD walking. At the ankle joint, flexion during the E2 phase (yield) of stance was minimal or absent for BWD walking, and ankle extension during BWD stance was accompanied by a ramp increase in LG-EMG activity. At the knee joint, the yield was also small (or absent) for BWD walking, and increased VL-EMG amplitudes were associated with the increased range of knee extension for BWD stance. 5. Although the uniarticular hip extensor (anterior biceps femoris, ABF) was active during stance for both directions, the hip flexed during BWD stance and extended during FWD stance.(ABSTRACT TRUNCATED AT 400 WORDS)

Adaptation, Physiological↗
PubMed1990

Scratch responses in normal cats: hindlimb kinematics and muscle synergies.

1. Scratch responses evoked by a tactile stimulus applied to the outer ear canal were characterized in nine adult cats. Chronic electromyographic (EMG) electrodes were surgically implanted in selected flexor and extensor muscles of the hip, knee, and ankle joints to determine patterns of muscle activity during scratching. In some trials EMG records were synchronized with kinematic data obtained by digitizing high-speed ciné film, and in one cat, medial gastrocnemius (MG) tendon forces were recorded along with EMG. For analysis the response was divided into three components: the approach, cyclic, and return periods. Usually scratch responses were initiated with the cat in a sitting position, but in some trials the animal initiated the response from a standing or lying posture. 2. During the approach period the hindlimb ipsilateral to the stimulated ear was lifted diagonally toward the head by a combination of hip and ankle flexion with knee extension. Hindlimb motions during the approach period were associated with sustained EMG activity in hip-flexor, knee-extensor (occasionally), and ankle-flexor muscles. Initial hindlimb motions were typically preceded by head movements toward the hindpaw, and at the end of the approach period, the head was tilted downward with the stimulated pinna lower than the contralateral ear. During the return period movements were basically the reverse of the approach period, with the hindpaw returning to the ground and the head moving away from the hindlimb. 3. During the cyclic period the number of cycles per response varied widely from 1 to 60 cycles with an average of 13 cycles, and cycle frequency ranged from 4 to 8 cycles/s, with a mean of 5.6 cycles/s. During each cycle the paw trajectory followed a fairly circular path, and the cycle was defined by three phases: precontact, contact, and postcontact. On average the contact phase occupied approximately 50% of the cycle and was characterized by extensor muscle activity and extension at the hip, knee, and ankle joints. The hindpaw contacted the pinna or neck at the base of the pinna throughout the contact phase, and paw contact typically resulted in a rostral motion of the head as the hindlimb extended. 4. The postcontact phase constituted approximately 24% of scratch cycle and was usually initiated by the onset of knee flexion. Ankle and then hip flexion followed knee flexion, and flexor muscles were active during the postcontact phase as the paw was withdrawn from the head. The precontact phase constituted approximately 26% of scratch cycle and was initiated by knee joint extension and knee-extensor activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

Mechanisms of neurulation: traditional viewpoint and recent advances.

In this review article, the traditional viewpoint of how neurulation occurs is evaluated in light of recent advances. This has led to the formulation of the following fundamentals: (1) neurulation, specifically neural plate shaping and bending, is a multifactorial process resulting from forces both intrinsic and extrinsic to the neural plate; (2) neurulation is driven by both changes in neuroepithelial cell shape and other form-shaping events; and (3) forces for cell shape changes are generated by both the cytoskeleton and other factors. Several cell behaviors within the neural plate have been elucidated. Future challenges include identifying cell behaviors within non-neuroepithelial tissues, determining how intrinsic and extrinsic cell behaviors are orchestrated into coordinated morphogenetic movements and elucidating the molecular mechanisms underlying such behaviors.

Animals↗
PubMed1990

Clinical and radiologic features of malignant neoplasms in organ transplant recipients: cyclosporine-treated vs untreated patients.

The radiologic and clinical features of 37 posttransplantation malignant tumors occurring in 33 organ transplant recipients were reviewed to determine the characteristics of the tumors, particularly in relation to previous treatment (or nontreatment) with cyclosporine. The 37 malignant tumors included lymphomas (eight in patients receiving cyclosporine and four in patients not given cyclosporine) and carcinomas of the skin and lips (11), head and neck (five), colon and rectum (three), uterus (two), vulva (two), lung (one), and urinary bladder (one). The neoplasms of the internal viscera and head and neck were relatively advanced when detected. The neoplasms of the skin, vulva, uterine cervix, and urinary bladder were low-grade malignant tumors. Most of the cyclosporine-induced malignant lesions were lymphomas. The lymphomas in cyclosporine-treated recipients were characterized by early appearance after transplantation; more extensive organ involvement; multiple, homogeneous solid lesions without central low density on CT and sonography; and regression after reduction of cyclosporine dose. We conclude that malignant tumors occurring after transplantation are often advanced and that lymphoma induced by cyclosporine has characteristic features.

Adult↗
PubMed1990

Effect of topical acid on pepsinogen secretion in man.

The stimulation of pepsinogen secretion by the presence of topical acid has previously been demonstrated in the dog (by a locally mediated, cholinergic mechanism) and suggested in man. The current experiments quantified the effect of luminal acid on pepsin secretion in man by using gastric instillations of acid solutions and recoveries with gastric washes. Solutions tested (pH 0.84-5.0) included buffered solutions, hydrochloric and acetic acid solutions, and an aspirin-acid solution. Decreasing pH or increasing acid concentration led to a significant increase in pepsin output, with a mean maximum increase of 70% over basal (pH 5.0) at the lowest pH (pH 0.84). The secretion of pepsin as a result of similar concentrations of hydrochloric or acetic acid did not differ, nor was pepsin secretion augmented by aspirin, used as a 'barrier breaker', and it was not related to calculated duodenal delivery of acid. Thus, any in vivo study of pepsin secretion should be interpreted in the light of the possible stimulatory contribution of acid.

Acetates↗
PubMed1990

Hepatic acyl-coenzyme A:cholesterol acyltransferase activity is decreased in patients with cholesterol gallstones.

Altered hepatic cholesterol metabolism has been implicated in the etiology of cholesterol gallstones. This hypothesis has been examined by determining acyl-coenzyme A:cholesterol acyltransferase (ACAT) activity in liver biopsies from 31 cholesterol gallstone patients and 12 control subjects. Hepatic ACAT activity in gallstone patients was decreased to one-third that in controls (P less than 0.001). No differences in hepatic homogenate or microsomal free and total cholesterol concentrations were observed between the two groups. However, marked increases in free (107%) and total (98%) cholesterol concentrations were found in the cytosolic fraction of liver biopsies from gallstone patients. The total phospholipid concentration of the liver homogenate fraction was unchanged in both groups; however, the microsomal total phospholipid concentration was reduced by 17% (P less than 0.01) in gallstone samples compared with controls. This difference did not result in a significantly increased microsomal cholesterol/phospholipid ratio for the gallstone group (0.180 +/- 0.030) compared with the control group (0.169 +/- 0.042). These results show that hepatic ACAT activity is significantly decreased in cholesterol gallstone patients. These changes in ACAT activity in livers of patients with cholesterol gallstones are consistent with the known increase in the amount of free cholesterol secreted in the bile of these patients. Thus, the changes in ACAT activity may contribute to the pathogenesis of cholesterol gallstones.

Adult↗
PubMed1990

Cogan's syndrome and seroreactivity to Lyme borreliosis.

We document the case of a young woman with bilateral nonluetic, interstitial keratitis, vestibuloauditory problems, and bilateral recurrent facial palsies, who had strongly positive serologic tests of Lyme borreliosis. To our knowledge, this is the first reported case of positive serologic tests for Borrelia burgdorferi in a patient with Cogan's syndrome.

Adult↗
PubMed1990

Syphiloma/gumma of the optic nerve and human immunodeficiency virus seropositivity.

A 68-year-old man developed the sudden onset of transient obscurations of vision in the right eye in November 1988. Two weeks later he noted floaters, photophobia, and blurred vision in the left eye. He presented with unilateral optic disc edema in the right eye. The left eye showed anterior uveitis but a normal optic disc. He was found to be violently seroreactive for Treponema pallidum infection and was also human immunodeficiency virus (HIV) seropositive. Ultrasonography confirmed the presence of a solid thickening of the anterior optic nerve sheath in the right eye. An interesting and dramatic response to penicillin therapy occurred. This is the first instance of a gumma or solid syphiloma of the optic nerve documented by ophthalmic ultrasonography.

Aged↗
PubMed1990

Optic nerve sheath distention in Leber's optic neuropathy and the significance of the "Wallace mutation".

We recently encountered a 27-year-old man who presented an atypical clinical picture of Leber's hereditary optic neuropathy: His family history was negative, visual loss continued steadily for over 8 months, circumpapillary microangiopathy was equivocal, the optic discs showed large physiologic cups, and both optic nerve sheaths were notably distended with increased subarachnoid fluid. The latter was confirmed by ultrasonography, computed tomography, and magnetic resonance imaging. The patient's asymptomatic brother also showed unimpressive circumpapillary microangiopathy in the fundi. The asymptomatic mother from France was then seen, and she showed classic circumpapillary microangiopathy in the fundi. Studies of mitochondrial DNA showed the classic point mutation at position 11778 as reported by Wallace in all three family members. Another patient previously seen with classic Leber's hereditary optic neuropathy recently had mitochondrial DNA studies along with three other affected family members and five unaffected family members in the maternal lineage. All nine of these individuals were completely normal at the Wallace locus. In fact, sequencing of the entire ND-4 gene from one affected individual revealed it to be perfectly normal at the amino acid level. The importance of obtaining quantitative ultrasonography and the 30 degrees test, and studying mitochondrial DNA in patients suspected of having Leber's optic nerve disease is emphasized.

Adult↗
PubMed1990

The Bascom Palmer Eye Institute Lyme/syphilis survey.

Serologic screening of patients for Lyme borreliosis began at the Bascom Palmer Eye Institute (BPEI) in September 1987. This report reviews the data on 641 sera from that date up to January 1, 1990. Initially only immunofluorescent (IFA) IgG and IgM titers were obtained. Because of increasing numbers of borderline and positive IFA tests, a Lyme enzyme linked immunosorbent assay (ELISA) was added in April 1988. Also, because of significant serologic cross reactivity in patients exposed to Treponema pallidum, rapid plasma reagin (RPR) and fluorescent treponemal antibody absorption (FTA-ABS) tests were added to the serologic screening panel. Of all sera tested, 10% showed reactive RPR tests and 22% showed reactive FTA-ABS tests. Lyme IFA IgG titers were greater than or equal to 1:64 in 17% of the sera, and Lyme ELISA tests were greater than 1.25 in 15% of the sera. Our experience agrees with reports that serum RPR or VDRL tests are nonreactive in Lyme borreliosis, and that false positive FTA-ABS tests can occur in Lyme borreliosis. The importance of getting all four tests--RPR, FTA-ABS, Lyme IFA IgG and IgM, and Lyme ELISA--in all patients suspected of spirochetal disease is emphasized.

Adolescent↗
PubMed1990

Adult respiratory distress syndrome during pregnancy and immediately postpartum.

From 1976 to 1983, the adult respiratory distress syndrome occurred in 14 patients during pregnancy or within a month postpartum. There were 8 survivors, giving a 43% mortality. All but 2 patients had obstetric-related precipitating events--labor problems, infections, eclampsia-toxemia, and obstetric hemorrhages. During emergency cesarean sections, 3 patients had respiratory problems that may have caused their respiratory distress syndrome. The average duration of mechanical ventilatory support was 16 days. Six patients had barotrauma with 1 patient sustaining an irreversible anoxic central nervous system injury. Infections were documented in 8 patients, 6 of whom had obstetric foci. There is a lack of information regarding the adult respiratory distress syndrome in this patient group. Though uncommon, it can cause substantial mortality and morbidity.

Adult↗