Biomedical subjects

M J Patterson

Publications and source records attributed to M J Patterson.

At least 19 recordsLinked to original sources

PubMed2002

Effect of induced metabolic alkalosis on sweat composition in men.

To determine whether induced metabolic alkalosis affects sweat composition, 10 males cycled for 90 min at 62.5 +/- 1.3% peak oxygen uptake, on two separate occasions. Subjects ingested either empty capsules (placebo) or capsules containing NaHCO3- (0.3 g kg-1 body mass; six equal doses) over a 2-h period, which commenced 3 h prior to exercise. Arterialized-venous blood samples were drawn prior to and after 15, 30, 60 and 90 min of exercise. Sweat was aspirated at the end of exercise from a patch located on the right scapula region. NaHCO3- ingestion elevated blood pH, [HCO3-] and serum [Na+], whereas serum [Cl-] and [K+] were reduced, both at rest and during exercise (P < 0.05). Sweat pH was greater in the NaHCO3- trial (6.24 +/- 0.18 vs. 6.38 +/- 0.18; P < 0.05), whereas sweat [Na+] (49.5 +/- 4.8 vs. 50.2 +/- 4.3 mEq L-1), [Cl-] (37.5 +/- 5.1 vs. 39.3 +/- 4.2 mEq L-1) and [K+] (4.66 +/- 0.19 vs. 4.64 +/- 0.34 mEq L-1) did not differ between trials (P > 0.05). Sweat [HCO3-] (2.49 +/- 0.58 vs. 3.73 +/- 1.10 mEq L-1) and [lactate] (8.92 +/- 0.79 vs. 10.51 +/- 0.32 mmol L-1) tended to be greater after NaHCO3- ingestion, although significance was not reached (P=0.07 and P=0.08, respectively). These data indicate that induced metabolic alkalosis can modify sweat composition, although it is unclear whether the secretory coil, reabsorptive duct, or both are responsible for this alteration.

Adult↗

PubMed2001

Metabolic habituation following repeated resting cold-water immersion is not apparent during low-intensity cold-water exercise.

This project examined the effects of repeated, resting cold-water immersion on metabolic heat production and core temperature defence during subsequent rest and exercising immersions. Seven males undertook 15 days of cold-water adaptation, immersed to the fourth intercostal space, with cold-water stress tests (CWST) on days 1, 8 and 15 (18.1 SD 0.1 degree C: 60 min seated, followed by 30 min cycling (1 W.kg-1)), and 90-min resting immersions (18.4 SD 0.4 degree C) on each of the intervening days. Adaptation elicited an habituated thermogenic response during the rest phase of CWST3 beyond 20 min, compared to CWST1 (P < 0.05), with oxygen consumption averaging 11.15 (+/- 0.25) ml.kg-1.min-1 and 8.61 (+/- 0.90) ml.kg-1.min-1 by 50 min, for CWST1 and CWST3, respectively. During exercise, this metabolic blunting was only apparent over the first 10-min period (60-70 min). No significant differences were observed during either the rest or exercise phases of the CWSTs for oesophageal temperature (Tes). While repeated cold-water exposures produced an habituated-thermogenic response, for an equivalent drop in Tes during rest, neither this response, nor an elevated thermogenesis, were apparent during subsequent cold-water exercise.

Adaptation, Physiological↗

PubMed2000

Ventricular remodeling after acute myocardial infarction: effect of low-intensity laser irradiation.

BACKGROUND AND OBJECTIVE: Low-intensity laser irradiation is claimed to enhance wound healing. Healing after myocardial infarction results in ventricular enlargement and wall thinning. If laser treatment accelerated cardiac healing, we speculated that ventricular remodeling would be attenuated. STUDY DESIGN/MATERIALS AND METHODS: In vitro, fibroblasts were irradiated for 1 minute twice a day for 4 days (5 mW; wavelength, 780 nm). One day after infarction, rats were randomly assigned to 5 or 10 mW transdermal irradiation twice a day for 4 days or to sham. One week after infarction, we measured the remodeling parameters; cavity volume, infarct thickness, and vascular structure, and the healing parameters; collagen content and inflammation. RESULTS: Laser-treated fibroblasts occupied more area than controls. Hearts receiving the 10 mW treatment had smaller volumes than sham hearts. Laser treatment reduced infarct thinning and preserved arterial lumen area; however, collagen was not increased and inflammation was inhibited. CONCLUSIONS: Low-intensity irradiation attenuated infarct-associated remodeling. In contrast to expectations from in vitro study, these effects were not a result of enhanced healing.

Animals↗

PubMed2000

Histologic signatures of thermal injury: applications in transmyocardial laser revascularization and radiofrequency ablation.

BACKGROUND AND OBJECTIVE: Cardiac treatments such as transmyocardial laser revascularization and radiofrequency ablation cause thermal injury. We sought to provide quantitative histologic methods of assessing such injury by using the inherent birefringence of cardiac muscle and collagen; specifically, to exploit the connection between thermal injury and the loss of birefringence. STUDY DESIGN/MATERIALS AND METHODS: We quantified tissue birefringence changes in vitro for temperatures up to 130 degrees C. This information was used to assess thermal injury associated with myocardial channels made in vitro. We then measured in vivo cardiac injury 30 minutes and 3 days after radiofrequency exposure. RESULTS: Birefringence decreased above 60 degrees C for muscle and above 70 degrees C for collagen. Temperatures above 80 degrees C were associated with collagen fiber straightening and above 95 degrees C with little muscle birefringence. Injury adjacent to laser channels was greatest parallel to cell orientation. In vivo, muscle with reduced birefringence was surrounded by cells exhibiting focal birefringence increases (contraction bands). Early injury assessment marked by birefringence changes corresponded to lesion size at 3 days. CONCLUSION: Polarized light revealed histologic temperature signatures corresponding to irreversible muscle injury and collagen denaturation.

Animals↗

PubMed2000

Osteogenic growth peptide normally stimulated by blood loss and marrow ablation has local and systemic effects on fracture healing in rats.

Osteogenic growth peptide, a histone H4-related, 14-amino-acid peptide, is an active mediator of local, as well as systemic, osteogenic activity in response to marrow ablation, trauma, and blood loss. In this study, the effect of exogenous osteogenic growth peptide on the healing of femoral fractures in rats was investigated. A fracture at the midshaft of the femur was created in 50 rats. Half of the rats were injected subcutaneously with 25 ng of osteogenic growth peptide per rat per day for the first 7 days after fracture. Radiographs were taken each week, and the diameter of the callus was measured. The femurs of four animals from each group were harvested 1, 2, 3, and 4 weeks after fracture. Two femurs from each group were sectioned for histologic examination, and two were sectioned for measurement of density and mineral content. Marrow was aspirated from the contralateral femurs to establish adhering cell cultures, which were examined for osteogenicity. At 2 weeks, a large increase in mitogenicity and osteogenicity was seen in the marrow-derived cultures from the rats treated with osteogenic growth peptide; this increase was sustained through 4 weeks. Extraction of RNA from the contralateral marrow (systemic expression) and callus (local expression) for amplification with reverse transcription-polymerase chain reaction revealed greater systemic expression of transforming growth factors beta1, beta2, and beta3, fibroblast growth factor-2, insulin-like growth factor-1, and aggrecan throughout the 4 weeks after fracture, whereas types IIA and IIB collagen, link protein, and fibroblast growth factor receptor-3 had a greater local expression. The specimens treated with osteogenic growth peptide had a stronger expression of transforming growth factor-beta1, both locally and systemically. The average diameter of the callus was greater for the treated rats at all time intervals, and peak diameters were 7.58 mm at 3 weeks for the treated rats and 6.64 mm at 2 weeks and 6.63 mm at 3 weeks for the controls. Histological study revealed an earlier organization and faster healing of the treated fractures, as evidenced by the larger, earlier appearance of cartilaginous soft callus and the more rapid organization of bridging trabecular bone. No statistical significance was obtained when these comparisons were made between the groups. These results suggest that osteogenic growth peptide can be used to promote earlier proliferation and differentiation of osteogenic cells in marrow and bone-repair callus, possibly through its effect on the transforming growth factor-beta family.

Animals↗

PubMed2000

Variations in regional sweat composition in normal human males.

This project aimed to quantify the regional distribution of sweat composition over the skin surface and to determine whether sweat constituent concentrations collected from regional sites can estimate whole-body concentrations. Ten males cycled for 90 min in a 20 degrees C (50% relative humidity) environment at 45% peak aerobic power. Sweat was collected from eleven skin regions and the whole body, using a wash-down technique. Strong relationships were evident between the regional and whole-body sweat [Na+] and [Cl-], such that the thigh and calf exhibited greater correlation coefficients than area-weighted means derived from four and eight skin regions. Therefore, in this particular protocol the whole-body sweat [Na+] and [Cl-] could be predicted from regional sweat collections. Relationships between sweat constituents were evident for sweat [Na+] and pH, and sweat [K+] and [lactate] when data were pooled between skin regions and subjects. To our knowledge this is the first investigation to report a positive relationship between sweat [K+] and [lactate]. The exact mechanism responsible for the positive relationship between sweat [K+] and [lactate] is uncertain although it is speculated to occur at the secretory coil.

Adult↗

PubMed2000

Pulmonary infections in the adolescent with immunodeficiency.

Pulmonary infections in the immunocompromised adolescent are important causes of significant morbidity and mortality. Advances in the fields of chemotherapy, organ transplantation, and use of corticosteroid and immunosuppressive therapies have led to significant improvement in the outcome of patients with malignancy and a variety of other disorders. HIV infection has become a major additional cause of immune suppression. In turn, physicians are encountering growing numbers of patients with an impaired immune system presenting with respiratory and other infections. This article presents a brief review of defense mechanisms in the respiratory tract, selected conditions leading to impaired immune responses in the adolescent, specific pulmonary pathogens and their evaluation in the immunocompromised adolescent, and general considerations of the management of pulmonary infections in the immunocompromised adolescent. Infections of the upper respiratory tract and pulmonary infections seen in adolescents with cystic fibrosis are not discussed.

Adolescent↗

PubMed1999

Peroneus longus tendon rupture as a cause of chronic lateral ankle pain.

Rupture of the peroneus longus tendon with an associated fracture of the os peroneum is an uncommon injury, which may present as chronic lateral ankle instability. There have been only seven cases documented in the literature since 1966. A case of chronic peroneus longus tendon rupture with os peroneum fracture is presented. The authors review their clinical, radiographic, and operative treatment of this patient and review the literature of this unusual injury.

Ankle Joint↗

PubMed1999

Two-staged delayed open reduction and internal fixation of severe pilon fractures.

OBJECTIVE: To evaluate the use of a two-staged technique for the treatment of C3 pilon fractures. DESIGN: Retrospective. SETTING: Level I trauma center. PATIENTS/PARTICIPANTS: Twenty-one consecutive patients with twenty-two C3 pilon fractures. Patients with C1 or C2 fractures and patients with open growth plates were excluded. INTERVENTION: All patients underwent immediate fibular fixation and placement of a medial spanning external fixator. After, on average, twenty-four days, patients underwent removal of the external fixator and formal open reduction and internal fixation of the pilon fractures. MAIN OUTCOME MEASUREMENTS: At average follow-up of twenty-two months, all patients were evaluated by using subjective, objective, and radiographic measurements as described by Burwell and Chamley (J Bone Joint Surg 1965;47B:634-659). Range of motion and postoperative complications were also recorded. RESULTS: Twenty-one of the twenty-two fractures healed within an average of 4.2 months. Average range of motion was 7 degrees of dorsiflexion, 33 degrees of plantar flexion, 17 degrees of eversion, and 11 degrees of inversion. Subjective and objective measurements showed 77 percent good results, 14 percent fair results, and 9 percent poor results. Radiographic reduction showed 73 percent anatomic and 27 percent fair reductions. There were no infections or soft tissue complications. The arthrodesis rate was 9 percent. CONCLUSIONS: A two-staged approach offers acceptable results for the treatment of severe pilon fractures. These results compare favorably with those of primary open reduction and of internal fixation and external fixation techniques. The major advantages include limited soft tissue complications and improved articular reconstruction.

Adult↗

PubMed1998

Human sudomotor responses to heating and cooling upper-body skin surfaces: cutaneous thermal sensitivity.

The influence of local skin temperature (Tskl) on the control of local and whole-body sweating was evaluated in eight healthy males. A water-perfusion garment (37 degrees C) and a climatic chamber (36.45 +/- 0.78 degrees C; [+/- SD]; relative humidity 60.3 +/- 1.6%) were used to raise and clamp skin and core temperatures. Warm and cool stimuli were applied to four upper-body skin regions (face, arm, forearm, hand) using perfusion patches (249.0 +/- 0.2 cm2). Heating elevated, while cooling suppressed sweat rate (msw) locally, and at other skin surfaces. However, the tendency for Tskl manipulations to induce localized sweat responses was no more powerful than it was at stimulating sweating in non-treated regions (P > 0.05). Accordingly, neither thermal stimulus produced significantly greater local sudomotor influences than were elicited contralaterally (P > 0.05). No statistical support was found for the notion of inter-regional differences in upper-body cutaneous thermal sensitivity for sudomotor control, and, regardless of the stimulation site, whole-body sudomotor responses to localized thermal treatments were equivalent (P > 0.05).

Acclimatization↗

PubMed1997

Sweat distribution before and after repeated heat exposure.

We investigated the impact of short-term, moderate humidity heat acclimation upon sweat distribution. Eight males completed six daily heat exposures [cycling: ambient temperature 39.5 (0.2) degrees C, relative humidity 59.2 (0.8)%], during which auditory canal temperature (T(ac)) was maintained 1.4 degrees C above pre-exposure levels for 70 min by manipulating the work rate. On days 1 and 6, T(ac) and local sweat rates (m(sw): eight sites) were monitored. The pre-exposure, resting T(ac) and the T(ac) sweat threshold decreased from day 1 to day 6 [36.83 (0.05) degrees C vs 36.62 (0.05) degrees C, and 36.90 (0.05) degrees C vs 36.75 (0.05) degrees C, respectively; both P < 0.05]. However, the sweat-onset time, sweat sensitivity (delta m(sw)/deltaT(ac)) and established m(sw) were unaltered (P > 0.05). There was also no evidence of a post-acclimation redistribution in established m(sw) between the eight skin regions, though both the sweat sensitivity and established m(sw) for the forehead and hand were significantly greater than at the remaining sites (P < 0.05). It is concluded that the 5-day heat acclimation regimen provided only a minimal stimulus for sudomotor adaptation.

Adaptation, Physiological↗

PubMed1997

Effects of artificially-induced anaemia on sudomotor and cutaneous blood flow responses to heat stress.

The influence of artificially induced anaemia on thermal strain was evaluated in trained males. Heat stress trials (38.6 degrees C, water vapour pressure 2.74 kPa) performed at the same absolute work rates [20 min of seated rest, 20 min of cycling at 30% peak aerobic power (VO2pcak), and 20 min cycling at 45% VO2peak] were completed before (HST1) and 3-5 days after 3 units of whole blood were withdrawn (HST2). Mild anaemia did not elevate thermal strain between trials, with auditory canal temperatures terminating at 38.5 degrees C [(0.16), HST1] and 38.6 degrees C [(0.13), HST2; P > 0.05]. Given that blood withdrawal reduced aerobic power by 16%, this observation deviates from the close association often observed between core temperature and relative exercise intensity. During HST2, the absolute and integrated forearm sweat rate (mSW) exceeded control levels during exercise (P < 0.05), while a suppression of forehead mSW occurred (P < 0.05). These observations are consistent with a possible peripheral redistribution of sweat secretion. It was concluded that this level of artificially induced anaemia did not impact upon heat strain during a 60-min heat stress test.

Adult↗

PubMed1997

A non-linear effect of ambient temperature on apparent glucose tolerance.

Increased ambient temperature affects apparent oral glucose tolerance to an extent which may have clinical implications for the diagnosis of impaired glucose tolerance and gestational diabetes. As a first step in order to better define the nature of this effect, we have examined, in a climate chamber, the effects of ambient temperature at four levels (20, 25, 30, and 35 degrees C) on glucose and insulin responses to a standard 75 g oral glucose tolerance test in seven non-diabetic male subjects. Plasma glucose responses to ambient temperature were compared with the responses of core (auditory canal) and skin temperatures. The 2-h plasma glucose was affected in a nonlinear manner by ambient temperature (5.4 +/- 0.2, 5.3 +/- 0.4, 6.5 +/- 0.3, 6.4 +/- 0.4 mmol/l at 20, 25, 30, and 35 degrees C, P = 0.015) with the effect localised between 25 and 30 degrees C (P = 0.012). Core temperature responded in a similar manner (36.6 +/- 0.1, 36.6 +/- 0.1, 36.9 +/- 0.1, 37.0 +/- 0.1, (P = 0.0005) with the effect localised 25 and 30 degrees C (P = 0.011). However skin temperature increased significantly with each 5 degrees C increase in ambient temperature (30.2 +/- 0.5, 33.0 +/- 0.5, 34.2 +/- 0.2, 35.2 +/- 0.2, P < or = 0.0001). We conclude that the acute effect of ambient temperature on apparent glucose tolerance is most likely due to redistribution of blood flow between cutaneous and visceral beds driven by changes in core temperature. The absence of temperature effects between the two lowest, and between the two highest temperatures, provides workable guidelines for the standardisation of conditions during oral glucose tolerance tests in circumstances where temperature may have clinically significant effects.

Adult↗

PubMed1997

Vestibular nerve pathology in cases of intractable vertigo: an electronmicroscopic study.

OBJECTIVE: This study aimed to determine the absence or presence and the nature of pathology of the vestibular nerve in case of intractable vertigo. STUDY DESIGN: This was a prospective study. SETTING: The study was performed at a private practice tertiary referral center. PATIENTS: There-were 42 patients with intractable vertigo in the study. INTERVENTIONS: All patients received thorough diagnostic examinations and surgical excision of the vestibular nerves. MAIN OUTCOME MEASURES: Segments of the superior and inferior vestibular nerves were surgically removed, preserved in glutaraldehyde, examined by electronmicroscopy, and the findings were correlated with the clinical diagnosis. RESULTS: A variety of different types of pathologic lesions were identified, including axon and supporting cell degeneration, herpes zoster virus, other viruses, results of bacterial infection, and regrowth of nerve after surgical resection. CONCLUSION: The vestibular nerves were found to be histologically normal in lesions primarily involving the end organ such as most early Meniere's disease cases, benign paroxysmal postural vertigo (BPPV), and mild labyrinthine concussion. Vestibular nerve degeneration was seen with advanced Meniere's disease, severe labyrinthine concussion, and with vascular loops in the internal auditory canal. Herpes zoster involves Scarpa ganglion in herpes zoster oticus. Viruses were found in the nuclei of vestibular nerve cells in a patient with delayed hydrops. Regrowth of the vestibular nerve after surgical resection was confirmed in three cases.

Adult↗

PubMed1995

The topography of eccrine sweating in humans during exercise.

The purpose of this study was to investigate the distribution of steady-state sweating rates (msw), during stressful exercise and heat exposures. Six men completed 42-min trials: 2-min rest and 40-min cycling at 40% peak power in 36.6 degrees C (relative humidity 46.0%). The msw was monitored using ventilated capsules at the forehead, and at three additional sites. Repeat trials allowed monitoring from eleven skin surfaces. Auditory canal temperature (Tac) and 11 skin temperatures were measured. After normalising msw to the forehead response within subjects, differences in Tac and onset time thresholds, and transient and steady-state msw were examined. The pooled, lower torso msw onset [mean 45.5 (SEM 42.0) s] preceded that of the head [mean 126.5 (SEM 34.8) s, P < 0.05], but was not significantly different from the legs [mean 66.6 (SEM 25.7) s], upper torso [mean 80.2 (SEM 36.8) s] or arms [mean 108.6 (SEM 31.2) s]. Transient msw did not differ among regions (P = 0.16). Mean, steady-state forehead msw [3.20 (SEM 0.51) mg.cm-2.min-1] was not significantly greater than the scapula, forearm, hand, stomach and lower back msw (in descending order), but was greater than the chest [1.6 (SEM 0.2)], upperarm [1.6 (SEM 0.2)], calf [1.5 (SEM 0.3)] and thigh msw [1.0 (SEM 0.2), P < 0.05 for all comparisons]. The results did not support the caudal-to-rostral sweat onset evident during supine, resting heat stress. Equivalent Tac sweat thresholds existed between sites, while steady-state state msw topography varied among subjects and was not dominated by central regions.

Adult↗

PubMed1995

Thermal tolerance following artificially induced polycythaemia.

Polycythaemia has been shown to improve physical performance, possibly due to increased arterial oxygen transport. Enhanced thermoregulatory function may also accompany this manipulation, since a greater proportion of the cardiac output becomes available for heat dissipation. We further examined this possibility in five trained men, who participated in three-phase heat stress trials (20 min rest, 20 min cycling at 30% peak power (Wpeak) and 20 min at 45% Wpeak at 38.3 (SEM 0.7) degrees C [relative humidity 41.4 (SEM 2.9)%]. Trials were performed during normocythaemia (control) and polycythaemia, obtained by reinfusion of autologous red blood cells and resulting in significant elevation of arterial oxygen transport. During the polycythaemic trials, the subjects demonstrated diminished thermal strain, as evidenced by a significant reduction in cardiac frequency (fc: 12 beats.min-1 lower throughout the test; P < 0.05), and reduced auditory canal temperatures (Tac) during the latter 20-min phase (P < 0.05). Forearm sweat onset was more rapid (363.0 compared to 1083.0 s; P < 0.05), and forearm sweat rate (msw) sensitivity was elevated from 1.80 to 2.91.mg.cm-2.min-1.degrees C-1 (P < 0.05). Forehead msw was depressed during the final 20 min, while forearm msw was greater during all test phases, averaging 0.94 and 1.20 mg.cm-2.min-1, respectively, over the 60 min. Skin blood flows for the upper back, upper arm and forearm were reduced (P < 0.05). Polycythaemia enhanced thermoregulation, through an elevation in forearm sweat sensitivity and msw, but not via increased cutaneous blood flow. These modifications occurred simultaneously with decreases in fc and Tac, resulting in greater thermal tolerance.

Adult↗

PubMed1994

Screening maternal serum alpha-fetoprotein levels and human parvovirus antibodies.

The association between gestational infection with human parvovirus (B19) and fetal loss has increased interest in this virus and demand for diagnostic testing. However, serological assays for B19 are not yet widely available. Maternal serum alpha-fetoprotein (MSAFP) testing is commonly used during the second trimester to screen for various fetal defects. We attempted to determine whether an elevated level of MSAFP would be an appropriate indication for B19-specific tests. Over a 26-month period, MSAFP tests were performed at Michigan State University for 21 392 women. Sera remaining after that testing were stored frozen. Of these, 22 cases samples--from women with MSAFP levels greater than 3.0 multiples of the median (MOM) and pregnancies that ended in fetal loss--and 44 matched control samples--from women with MSAFP levels greater than 0.4 and less than 2.2 MOM and live births at term--were tested for B19 antibodies. None of the 66 samples was IgM positive, while 33 (50 per cent) were IgG positive. The presence of IgG was not significantly associated with case or control status (matched odds ratio = 0.77, 95 per cent confidence interval 0.28-2.11). These findings are consistent with other studies indicating prior infection in approximately half of adults and suggest that elevated screening MSAFP levels, in the absence of other evidence of B19 infection, should not prompt B19-specific testing.

Adult↗

PubMed1994

Attenuation of the cutaneous blood flow response during combined exercise and heat stress.

Skin blood flow (SkBF) was measured in six male subjects using laser-Doppler velocimetry, with zero-gradient auditory canal temperature (Tac) used as an index of body core temperature (Tc). Subjects performed incremental, upright cycling commencing at 40% peak power (Wpeak: 10 min), increasing every 4 min by 5% Wpeak thereafter. Trials were conducted in hot (ambient temperature (Ta) 36.7 +/- 0.2 degree C, relative humidity (rh) 46.1 +/- 3.2%; mean +/- S.D.), and neutral environments (Ta 19.6 +/- 0.3 degree C, rh 50.2 +/- 1.4%). SkBF increased with Tac in all subjects. Attenuation of SkBF occurred at the same Tac, relative SkBF and cardiac frequency (fc) between environments, but at a lower exercise intensity (40.8 +/- 0.8% versus 55.8 +/- 3.0% Wpeak) in the hot environment (p < 0.05). Data indicate that Tc thresholds for SkBF attenuation may exist. However, it is suggested that attenuation thresholds coincided with a reduced central blood volume, which may occur at a critical level of cutaneous blood pooling.

Adult↗