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Biomedical subjects

R J Nelson

Publications and source records attributed to R J Nelson.

At least 235 records · Page 13Linked to original sources
PubMed1987

Measurement of total circulating blood volume following subarachnoid haemorrhage: methodological aspects.

The total circulating blood volume (TCBV) and total body/venous haematocrit ratio (Htb/Hv) was determined by simultaneous measurement of the red cell volume (RCV) and the plasma volume (PV) in 10 subarachnoid haemorrhage (SAH) patients, 10 supine bedresting control patients and 20 ambulant out-patients. The mean Htb/Hv of the SAH patients, 0.866, was found to be significantly lower than that of the supine controls, 0.908, and the ambulant patients, 0.909, (p less than 0.01). Using the ratio 0.866 the total circulating blood volume of the SAH patients was calculated from either their RCV or their PV and compared with their measured TCBV. Expressed as a percentage of measured TCBV the mean errors of these single volume determinations were 2.84% and 1.76% respectively. The significance of these changes in the Htb/Hv ratio of SAH patients is discussed in relation to the circulatory disturbances they suffer.

Adult↗
PubMed1987

Reproductive response of a tropical mammal, the musk shrew (Suncus murinus), to photoperiod.

Musk shrews (Suncus murinus) were maintained for 8 weeks in long (16 h light:8 h darkness) or short (8 h light:16 h darkness) daylengths. Males housed in short daylength had significantly lighter androgen-dependent sex accessory organs than did males kept in long daylengths. This same trend was noted in male sexual behaviour. However, the weights of the testes and epididymides and sperm numbers did not differ. Females housed in short daylengths had significantly lighter cervices and were less likely to demonstrate sex behaviour than animals kept in under long daylengths. Ovarian and uterine weights did not differ. These results suggest that the ability to respond to photoperiod can exist in tropical mammals, even if it is not used as a cue to time seasonal breeding.

Animals↗
PubMed1986

Functional reorganization in somatosensory cortical areas 3b and 1 of adult monkeys after median nerve repair: possible relationships to sensory recovery in humans.

Previous studies have shown that the primary somatosensory cortex of adult mammals undergoes somatotopic reorganization in response to peripheral nerve transection. The present study assesses how cortical organization is affected when a transected nerve subsequently regenerates. The median nerve to one hand of adult owl monkeys was transected and repaired. Following nerve regeneration, the representations of the hand in cortical areas 3b and 1 were studied with neurophysiological mapping methods. The major results were as follows: Peripherally, median nerve transection, repair, and regeneration resulted in reinnervation of the median nerve skin territory. Centrally, both the initial loss and subsequent regeneration of median nerve inputs caused reorganizational changes in cortex. Reorganizational changes were specifically restricted to regions of the hand cortex where inputs from the median nerve were normally represented. The functional features of cortical regions that recovered tactile responsiveness from reinnervated skin regions were abnormal in several respects. Most notably, these regions contained recording sites with abnormally located or multiple cutaneous receptive fields, and contained major topographical changes, such as reestablishment of palmar pad or digit representations in small, discontinuous patches of cortex. Normal organizational features were reestablished to a more limited extent. These features included recovery of delimited, discrete receptive fields and reestablishment of topographic representations for localized skin areas. Different transformations in topographical organization were seen in areas 3b and 1 of the same monkey. These results suggest that nerve regeneration reestablishes the cortical capacity to process tactile information from reinnervated skin via a prolonged reorganizational process that appears dependent on peripheral and central factors. Cortical recovery mechanisms clearly appear to have limitations, since preinjury patterns of cortical organization are not widely recovered even almost 1 year after repair. We suggest possible relationships between cortical reorganizational changes in these primates, and postrepair sensory changes in humans.

Animals↗
PubMed1985

Photoperiodic regulation of reproductive development in male prairie voles: influence of laboratory breeding.

Two populations of male prairie voles, one derived from an outbred laboratory colony and the second consisting of F1 offspring of wild-trapped voles, were tested for responsiveness to photoperiod. Animals were reared from birth until 35 days of age either in 16L:8D or 8L:16D photoperiods. Short day lengths did not affect the reproductive apparatus of the laboratory-strain voles; however, offspring of wild-caught voles manifested arrested development of the reproductive system in short photoperiods. These results suggest that selection processes associated with laboratory husbandry can alter responsiveness to photoperiod; the use of wild-trapped animals or their F1 progeny is indicated in photoperiodism research.

Animals↗
PubMed1985

Photoperiod influences reproduction in the prairie vole (Microtus ochrogaster).

Four experiments examined the role of photoperiod in the regulation of seasonal breeding in the prairie vole. Adult male voles maintained in short (8L:16D) as compared to long (16L:8D) photoperiods for 10 wk had reduced testicular and seminal vesicle weights, but fertility was not impaired. Male prairie voles reared from birth until 35 days of age in short as compared to long photoperiods also had reduced testicular and seminal vesicle weights, as well as diminished fertility. The incidence of pregnancy did not differ between long- and short-day female voles paired for 6 days with long- or short-day males (93%, 86%, 89%, and 88%, respectively). Photoperiod did not affect the incidence or the timing of postpartum pregnancies in long- or short-day females paired with long-day males through the birth of several litters. Adult male prairie voles retain only marginal sensitivity to short photoperiods, maturing males are highly responsive to short days, and adult females are insensitive to photoperiod. These data suggest that termination of the breeding season in the autumn may be due to the lack of fecund males in the population.

Animals↗
PubMed1985

Chemosensory and neural influences on photoperiodic responsiveness of laboratory rats.

Olfactory bulbectomy unmasks photoperiodic responsiveness in normally nonphotoperiodic rats. We assessed whether the photoperiodic effects of bulbectomy reflect disruption of chemosensory input. At 26-28 days of age, male Sprague-Dawley rats were subjected to removal of their vomeronasal organ (VNO) complex, a sham-VNO ablation or large electrolytic lesions aimed at the pyriform cortex or corticomedial nuclei of the amygdala. Other rats were infused with (1) 7.5% ZnSO4, a treatment that destroys the olfactory neuroepithelium, (2) 0.09% saline, or (3) air in each external nare every 4 days; rats from each treatment condition were assigned either to a long (LD 14:10) or short (LD 8:16) day lighting regimen and were autopsied at 90 days of age. Seminal vesicle and paired testes weights did not differ significantly among long-day groups. Mean seminal vesicle and paired testes weights were decreased only in short-day rats treated with ZnSO4. These results indicate that the VNO does not mediate the effects of photoperiod on rat reproduction. Olfactory information, not transduced by the amygdala, or nonsensory components of the olfactory bulbs appear to mask photoperiodism in intact rats.

Amygdala↗
PubMed1985

Neuroendocrine responsiveness to oestradiol and male urine in neonatally androgenized prairie voles (Microtus ochrogaster).

The influence of neonatal androgenization on behavioural receptivity was tested by treating female voles on the 3rd day of life with testosterone propionate or with the oil vehicle. After treatment in adulthood with urine or with oestradiol benzoate, androgenized voles were less likely than normal females to display behavioural oestrus and were more likely to engage in agonistic behaviour in tests with stud males. Uteri of androgenized and control females treated with oestradiol benzoate in adulthood manifested similar increases in weight; however, only normal females treated with male urine showed increased uterine weights. Males castrated in adulthood did not display lordosis after treatment with oestradiol benzoate. Sexual differentiation induced by neonatal testicular secretions appears to limit responsiveness of the adult neuroendocrine axis to chemosensory stimuli in male urine.

Animals↗
PubMed1984

Responsiveness of monkey primary somatosensory cortical neurons to peripheral stimulation depends on 'motor-set'.

Responses evoked by vibrotactile stimuli in primary somatosensory cortical neurons were studied under two conditions. In the first, the vibrotactile stimulus was the trigger for a movement of the stimulated hand, while in the second, the motor response had been extinguished. Thus, responses of the same neuron could be compared during different motor sets. Neurons in area 3a and 1, but not area 3b, often exhibited different responses depending on motor set. These findings support the view that responses of many somatosensory cortical neurons are modulated by central as well as peripheral influences and are dependent upon the context in which the stimulus occurs.

Animals↗
PubMed1984

The somatotopic organization of the ventroposterior thalamus of the squirrel monkey, Saimiri sciureus.

Multiunit microelectrode mapping techniques were used to investigate the organization of the somatosensory thalamus in squirrel monkeys. Receptive fields and response characteristics were determined for closely spaced recording sites along arrays of electrode penetrations that passed through the ventral thalamus dorsoventrally, rostrocaudally, or lateromedially. The results were related to thalamic architecture and led to the following conclusions: (1) A large, single, systematic representation of the body surface occupied most or all of the ventroposterior nucleus, VP. The nucleus was further defined by a distinct cytoarchitectonic appearance, produced by densely packed, deeply stained neurons. (2) Recording sequences in VP were characterized by (a) abrupt shifts in receptive field locations over short recording distances indicating that the electrode had crossed discontinuities or folds in the representation, (b) long sequences of overlapping receptive fields indicating regions of continuous representation and the maintenance of adjacency in the map, and (c) similar receptive field locations for sites along the trajectory of a penetration indicating regions of isorepresentation. Major somatotopic discontinuities were associated with crossing narrow cell-poor laminae that partially divided VP into subnuclei related to the hand, foot, trunk, and tail in lateral VP and the face in medial VP. Somatotopic discontinuities occurred for electrode penetrations in all three planes, but discontinuities were greater and more frequent for lateromedial electrode penetrations. Lines of isorepresentation and gradual change were most extensive in the rostrocaudal and dorsoventral planes. We hypothesize that the disruptions, regions of isorepresentation, and regions of gradual change result from the thickening, splitting, and folding of a two-dimensional representation of the skin surface to occupy a three-dimensional volume. (3) The magnifications of various skin surfaces in VP were variable so that some skin surfaces, especially the tips of the digits, occupied relatively large portions of the nucleus, while other skin surfaces such as the trunk activated little tissue. It appeared that regions of isorepresentation varied in extent according to magnification factor and position in the map. (4) Within VP, neurons could be classified as slowly adapting or rapidly adapting to maintained skin indentation. Each type of neuron formed small groups or clusters in the nucleus so that several successive recording sites typically encountered one type before a sequence of the other type was observed.(ABSTRACT TRUNCATED AT 400 WORDS)

Afferent Pathways↗
PubMed1984

Somatosensory cortical map changes following digit amputation in adult monkeys.

The cortical representations of the hand in area 3b in adult owl monkeys were defined with use of microelectrode mapping techniques 2-8 months after surgical amputation of digit 3, or of both digits 2 and 3. Digital nerves were tied to prevent their regeneration within the amputation stump. Successive maps were derived in several monkeys to determine the nature of changes in map organization in the same individuals over time. In all monkeys studied, the representations of adjacent digits and palmar surfaces expanded topographically to occupy most or all of the cortical territories formerly representing the amputated digit(s). With the expansion of the representations of these surrounding skin surfaces (1) there were severalfold increases in their magnification and (2) roughly corresponding decreases in receptive field areas. Thus, with increases in magnification, surrounding skin surfaces were represented in correspondingly finer grain, implying that the rule relating receptive field overlap to separation in distance across the cortex (see Sur et al., '80) was dynamically maintained as receptive fields progressively decreased in size. These studies also revealed that: the discontinuities between the representations of the digits underwent significant translocations (usually by hundreds of microns) after amputation, and sharp new discontinuous boundaries formed where usually separated, expanded digital representations (e.g., of digits 1 and 4) approached each other in the reorganizing map, implying that these map discontinuities are normally dynamically maintained. Changes in receptive field sizes with expansion of representations of surrounding skin surfaces into the deprived cortical zone had a spatial distribution and time course similar to changes in sensory acuity on the stumps of human amputees. This suggests that experience-dependent map changes result in changes in sensory capabilities. The major topographic changes were limited to a cortical zone 500-700 micron on either side of the initial boundaries of the representation of the amputated digits. More distant regions did not appear to reorganize (i.e., were not occupied by inputs from surrounding skin surfaces) even many months after amputation. The representations of some skin surfaces moved in entirety to locations within the former territories of representation of amputated digits in every monkey studied. In man, no mislocation errors or perceptual distortions result from stimulation of surfaces surrounding a digital amputation.(ABSTRACT TRUNCATED AT 400 WORDS)

Afferent Pathways↗
PubMed1984

Pulmonary embolism secondary to venous thrombosis of the arm.

Pulmonary embolism is described as an infrequent complication of axillary and subclavian vein thrombosis. We have reported our recent clinical experience with 14 patients admitted to the Harbor-UCLA Medical Center who had a clinical diagnosis of axillary and subclavian vein thrombosis documented by phlebography of the thrombosed arm. The causes of thrombosis were effort (three patients), trauma (three patients), drug abuse (four patients), underlying neoplastic disease (three patients), and congenital venous malformation (one patient). Pulmonary emboli were diagnosed by arteriogram, ventilation perfusion scans, and arterial blood gas abnormalities in five patients with respiratory symptoms for an incidence of 35.7 percent. Immediate anticoagulation with heparin, then switching to warfarin sulfate after 5 days, was the standard therapy in all patients. Follow-up examinations between 3 and 24 months demonstrated mild postphlebitic syndrome consisting of pain and minimal swelling in two patients. We conclude that pulmonary emboli may be a more frequent complication of axillary and subclavian vein thrombosis than has generally been recognized.

Adolescent↗
PubMed1984

Pregnancy interruption in Microtus ochrogaster: laboratory artifact or field phenomenon?

Females of at least 8 species of rodent will terminate pregnancies after exposure to a "strange" male or his odors in the laboratory. Although only suggestive evidence exists for the occurrence of pregnancy interruption in the field, this laboratory phenomenon has been assigned important adaptive roles in the reproductive biology of rodents. In the present study, the extent of pregnancy interruption was investigated for prairie voles (Microtus ochrogaster) in semi-natural enclosures where continued close proximity to males or their stimuli was not necessarily enforced upon females. Heterosexual pairs of voles were housed together in large, out-of-doors enclosures. After 10 days either 1) the original pair remained together for 30 additional days, 2) the stud male was replaced with a strange male for 30 days during which time the stud male was absent, or 3) the stud male was allowed to remain with the female, but another male was also added. Other heterosexual pairs of voles were placed in small cages typical of previous laboratory studies; 10 days later, the original male was replaced by a strange male. Dates of parturition were recorded. The data indicate that pregnancy interruption can occur in situations where 1) the female can potentially avoid the strange male, 2) the female can repel the strange male via aggressive behavior, or 3) the stud male is present to defend his mate. The findings of this study are discussed in relation to the possible adaptive significance of pregnancy block for small rodents.

Adaptation, Physiological↗
PubMed1984

Traumatic myocardial dysfunction.

Traumatic myocardial dysfunction is a frequently unsuspected, undiagnosed contributor to deaths from trauma. Electrocardiography, serum enzymes, and radionuclide myocardial scans are insensitive indicators of cardiac injury following blunt chest trauma. First-pass biventricular radionuclide angiography can accurately determine right and left ventricular ejection fractions and assess left ventricular segmental wall motion. Since August, 1980, we have evaluated 74 consecutive patients with blunt chest and multisystem trauma. Electrocardiograms and measurements of the myocardial band isoenzyme of creatine kinase were obtained at admission and repeated at 24 hour intervals for 3 days. Radionuclide angiography was performed 24 to 48 hours after admission. The electrocardiogram was abnormal in 21 patients (28%), levels of creatine kinase isoenzyme were elevated in six, and radionuclide angiographic abnormalities were present in 55 patients (74%). Electrocardiographic abnormalities correlated anatomically with angiographic abnormalities in 16 patients (76%). On follow-up radionuclide angiography, abnormalities had disappeared in nine of 12 patients restudied at 3 weeks. This study documents that the electrocardiogram and creatine kinase isoenzyme elevations are static, insensitive indicators of traumatic myocardial dysfunction. Radionuclide angiography with studies of left ventricular segmental wall motion demonstrate that traumatic myocardial dysfunction, although sometimes transitory, is a dynamic phenomenon that is more common than previously suspected. First-pass radionuclide angiography and wall motion studies are practical and valuable adjuncts to the management of the injured patient.

Adult↗
PubMed1984

Favorable ten-year experience with valve procedures for active infective endocarditis.

We have reviewed our 1972 to 1982 experience with valve procedures for infective endocarditis in 52 consecutive patients to evaluate the results of an interdisciplinary policy of early operation for uncontrolled complications. There were 47 patients with native valve endocarditis and five with prosthetic valve endocarditis. Twenty-seven were drug addicts and 25 were not. Thirty-seven (71%) required operation during the active phase of the disease and 15 during the inactive phase. Ninety-three percent of the addicts, 41% of the nonaddicts, and all patients with prosthetic valve endocarditis were in the active group. The distribution of infected valves was as follows: aortic, 21 active and 10 inactive; mitral, six active and three inactive; aortic and mitral, five active and two inactive; aortic and tricuspid, one active and none inactive; and tricuspid, four active and none inactive. Streptococcus was the most common infecting organism in both groups--predominantly group D in addicts and non-D in nonaddicts. Staphylococcus, gram-negative rods, and fungi occurred only in the active group. Indications for operation were congestive heart failure alone (19 active and 15 inactive), congestive heart failure and refractory infection or major emboli (nine active and none inactive), and resistant or refractory infection alone or with emboli (nine active and none inactive). Periannular abscess or aneurysm formation was most frequent at the aortic valve site in patients with native valve endocarditis; it occurred in 13 of 25 patients (52%) in the active group and in one of 12 patients (8%) in the inactive group. Six patients with preoperative stroke syndromes underwent operation without neurological deterioration; two patients had rupture of cerebral mycotic aneurysms postoperatively. Hospital mortality was 8% (3/7) in the active group and 0% in the inactive group. The late actuarial survival rate was 64% at 5 years and 54% at 10 years. Seven of nine deaths in the addict group were related to continued drug use, with five deaths occurring in the first 18 months. These results support a policy of early operation for uncontrolled complications with attention to the particular problems of active endocarditis.

Actuarial Analysis↗
PubMed1983

Representations of the body surface in areas 3b and 1 of postcentral parietal cortex of Cebus monkeys.

The somatotopic organization of postcentral parietal cortex was determined with microelectrode mapping methods in a New World monkey, Cebus albifrons. As in previous studies in macaque, squirrel and owl monkeys, two separate representations of the body surface were found in regions corresponding to the architectonic fields 3b and 1. The two representations were roughly mirror-images of each other, with receptive field locations matched for recording sites along the common border. As in other monkeys, the glabrous digit tips of the hand and foot pointed rostrally in the Area 3b representation and caudally in the Area 1 representation. Both representations proceeded in parallel from the tail on the medial wall of the cerebral hemisphere to the teeth and tongue in lateral cortex along the Sylvian fissure. Compared with the other monkeys, the tail of the cebus monkey, which is prehensile, was represented in a very large region of cortex in Areas 3b and 1. Like its close relative, the squirrel monkey, the representation of the trunk and parts of the limbs were reversed in orientation in both Area 3b and Area 1 in cebus monkeys as compared to owl and macaque monkeys. The reversals of organization for some but not all parts of the representations in cebus and squirrel monkeys suggest that one line of New World monkeys acquired a unique but functionally adequate pattern of somatotopic organization for the two adjoining fields.

Animals↗
PubMed1983

Myocardial dysfunction following blunt chest trauma.

We prospectively studied 35 patients with blunt chest trauma using ECG multi-gated and first-pass nuclear angiography. Radionuclide angiography (RNA) is a sensitive test of myocardial function demonstrating right and left ventricular ejection fractions. First-pass angiography, in addition, shows left ventricular segmental wall motion, a qualitative as well as anatomic indicator of left ventricular function. We saw RNA abnormalities in 26 patients (74.2%). Eight patients (22.8%) had ECG abnormalities, and these findings correlated with RNA, suggesting that this technique is a very sensitive indicator of myocardial dysfunction following trauma. These studies warrant further experimental and clinical evaluations to determine the cause, significance, and long-term prognosis of posttraumatic myocardial dysfunction.

Adult↗
PubMed1983

Rhythms of barbiturate-induced sleep time in deermice entrained to non-twenty-four hour photocycles.

The present experiment examined whether entrainment to twenty-four hour days is advantageous for physiological and behavioral adaptations to a pharmacological challenge. Adult, male deermice (Peromyscus maniculatus) were injected with sodium pentobarbital at 8.5, 14.5, 20.5, 2.5 and again at 8.5 hr after light onset while entrained to a 24 hr day (light/dark (LD) 14:10). Time to recover from anesthesia was recorded. Subsequently, the dark phase of the LD cycle was reduced 15-20 min every 10 days until a 23 hr photocycle was achieved, (LD 14:9; T = 23 hr). Injections of sodium pentobarbital were again administered at 8.5, 14.5, 20.5 and 2.5 hr after light onset and sleep times recorded. This procedure was repeated at T = 21 hr (LD 14:7) and T = 18 hr (LD 14:4). A variation in sleep time was observed during entrainment to all T-cycles except T = 18 hr. Sleep time after drug administration was generally longer during the light than during the dark phase of each photocycle. Recovery from anesthesia was not compromised in mice entrained to photocycles with periods of 23 or 21 hr; however, entrainment to very short days disrupted the normal pattern of response to barbiturate administration. Entrainment to a range of daylengths that deviate appreciably from 24 hr is consistent with normal physiological function.

Animals↗