Seafloor primary production in a changing Arctic Ocean

Phytoplankton and sea ice algae are traditionally considered to be the main primary producers in the Arctic Ocean. In this Perspective, we explore the importance of benthic primary producers (BPPs) encompassing microalgae, macroalgae, and seagrasses, which represent a poorly quantified source of Arctic marine primary production. Despite scarce observations, models predict that BPPs are widespread, colonizing ~3 million km2 of the extensive Arctic coastal and shelf seas. Using a synthesis of published data and a novel model, we estimate that BPPs currently contribute ~77 Tg C y-1 of primary production to the Arctic, equivalent to ~20 to 35% of annual phytoplankton production. Macroalgae contribute ~43 Tg C y-1, seagrasses contribute ~23 Tg C y-1, and microalgae-dominated shelf habitats contribute ~11 to 16 Tg C y-1. Since 2003, the Arctic seafloor area exposed to sunlight has increased by ~47,000 km2 y-1, expanding the realm of BPPs in a warming Arctic. Increased macrophyte abundance and productivity is expected along Arctic coastlines with continued ocean warming and sea ice loss. However, microalgal benthic primary production has increased in only a few shelf regions despite substantial sea ice loss over the past 20 y, as higher solar irradiance in the ice-free ocean is counterbalanced by reduced water transparency. This suggests complex impacts of climate change on Arctic light availability and marine primary production. Despite significant knowledge gaps on Arctic BPPs, their widespread presence and obvious contribution to coastal and shelf ecosystem production call for further investigation and for their inclusion in Arctic ecosystem models and carbon budgets.

Psychological vulnerability as a predictor for short-term outcome in lumbar spine surgery. A prospective study (Part II)

A prospective survey of the outcome following lumbar spine surgery was carried out during a period of six months. Of a consecutive series of 144 patients 130 cases (90%) could be evaluated. Postoperative follow-up was for six months. A test of psychological vulnerability was included with the preoperative data. Outcome was determined as unsatisfactory in case of re-operation (9%) before follow-up or if pain persisted unchanged or became worse (30%). Psychological vulnerability was significantly associated with poor outcome irrespective of age, sex, pre-operative somatic health, and surgical findings. The relative risk ratio of persisting pain attributable to psychological vulnerability was 1.8. The finding support the contention that psychogenic factors independently and significantly contribute to the multiple factor interaction that determines short-term outcome. The social consequences were strongly associated with psychological vulnerability. Among patients pre-operatively on sick-leave the relative risk ratio of unemployment attributable to psychological vulnerability was 6.0.

Short-term outcome in lumbar spine surgery. A prospective study (Part I)

A prospective survey of the outcome of lumbar surgery was carried out under conditions where all intervention was according to routine procedures. Of a consecutive series of patients 132 cases (92%) could be evaluated. The aim was to investigate possible predictive factors among self-reported data and clinical data readily available under routine circumstances. Follow-up was for six months post-operatively. Surgical findings were: herniated disc (62%), osteochondrosis (21%), other pathology (7%), and negative findings (10%). Unsatisfactory outcome was either relapse, operation before follow-up (9%) or persisting pain (30%). The surgical finding of a disc herniation predicted a significantly better outcome than any other finding. Cases previously operated upon (20%) fared equal with those operated upon for the first time irrespective of surgical findings. Self-reported weighting of preoperative pain and its location showed that predominant sciatica was significantly associated with the finding of a disc herniation, but also with satisfactory outcome irrespective of the operative finding. Factors without predictive value included sex, age, number of prior back surgeries, duration and impact of symptoms, and clinical findings. The social consequences were associated with the duration of low back disease.

Do concentrations of neurotransmitters measured in lumbar cerebrospinal fluid reflect the concentrations at brain level?

CSF concentrations of vasoactive intestinal polypeptide (VIP), cholecystokinin (CCK), noradrenaline (NA) and dopamine (DA) were measured in the lateral ventricles and at the lumbar level in patients with normal pressure hydrocephalus (NPH). The concentrations of VIP (n = 15), NA (n = 10) and DA (n = 10) were significantly higher at the lumbar level than at the ventricular level, whereas the concentrations of CCK (n = 9) were similar at the two sites. A significant positive correlation between the concentrations measured at the two levels was found for VIP (rs = 0.65; p less than or equal to 0.01) and DA (rs = 0.94; p less than or equal to 0.001). The results indicate that the concentrations of transmitter substances measured in CSF at the lumbar level not necessarily are indicative for concentrations measured more centrally. The negative correlations between Evans ratio and L-CSF VIP (rs = -0.76; p less than or equal to 0.001), and between resistance to outflow and V-CSF as well as L-CSF CCK (rs = -0.75); p less than or equal to 0.05) might be explained by a reduction in number of cortical neurons or by disturbances in CSF dynamics in patients with NPH.

The prognosis in subarachnoid hemorrhage of unknown etiology

The mortality rate, risk of rebleeding, relevant subjective and objective symptoms, and daily functional capacity after a verified subarachnoid hemorrhage (SAH) of unknown etiology were evaluated in 44 patients treated during a 5-year period (1978 to 1983). A vascular basis for the SAH had been excluded by bilateral carotid and vertebral angiography and computerized tomography. The patients were interviewed at a follow-up examination from 3 to 64 months (median 36 months) after the bleed. The results revealed a 5% mortality rate and a 7% risk of rebleeding. Persisting headache and fatigue were found in 40% of patients, 29% had mild demential symptoms, and 5% had persisting and severe objective neurological symptoms. None had developed epilepsy. A normal daily functional capacity was enjoyed by 84%, while 14% had a moderate reduction in these functions, but were independent of help from other persons. One patient (2%) was not fully assessed.